fix: remove build tags

[andorsk]

related to lestrrat-go/jwx#670 "You don't need to add build tags to your source code.".

[andorsk]

Note: the failure of the build is happening even on the main branch. Not sure what's going on with the build system, but I don't think this is related to the PR.

➜  ssi-sdk git:(main) mage test
[test -race -tags=jwx_es256k ./...]ok  	github.com/TBD54566975/ssi-sdk/credential	(cached)
ok  	github.com/TBD54566975/ssi-sdk/credential/exchange	(cached)
time="2022-07-04T10:42:39+05:30" level=error msg="credential manifest not valid against schema" error="Could not read schema from HTTP, response status is 404 Not Found"
time="2022-07-04T10:42:39+05:30" level=error msg="credential manifest not ready to be built" error="manifest failed json schema validation: Could not read schema from HTTP, response status is 404 Not Found"
time="2022-07-04T10:42:40+05:30" level=error msg="credential manifest not valid against schema" error="Could not read schema from HTTP, response status is 404 Not Found"
time="2022-07-04T10:42:40+05:30" level=error msg="credential manifest not ready to be built" error="manifest failed json schema validation: Could not read schema from HTTP, response status is 404 Not Found"
--- FAIL: TestCredentialManifestBuilder (2.43s)
    builder_test.go:102:
        	Error Trace:	builder_test.go:102
        	Error:      	Received unexpected error:
        	            	Could not read schema from HTTP, response status is 404 Not Found
        	            	manifest failed json schema validation
        	            	github.com/TBD54566975/ssi-sdk/credential/manifest.(*CredentialManifest).IsValid
        	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/model.go:36
        	            	github.com/TBD54566975/ssi-sdk/credential/manifest.(*CredentialManifestBuilder).Build
        	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/builder.go:34
        	            	github.com/TBD54566975/ssi-sdk/credential/manifest.TestCredentialManifestBuilder
        	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/builder_test.go:101
        	            	testing.tRunner
        	            		/usr/local/go/src/testing/testing.go:1439
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_arm64.s:1263
        	            	credential manifest not ready to be built
        	            	github.com/TBD54566975/ssi-sdk/util.LoggingErrorMsg
        	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/util/errors.go:24
        	            	github.com/TBD54566975/ssi-sdk/credential/manifest.(*CredentialManifestBuilder).Build
        	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/builder.go:35
        	            	github.com/TBD54566975/ssi-sdk/credential/manifest.TestCredentialManifestBuilder
        	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/builder_test.go:101
        	            	testing.tRunner
        	            		/usr/local/go/src/testing/testing.go:1439
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_arm64.s:1263
        	Test:       	TestCredentialManifestBuilder
    builder_test.go:103:
        	Error Trace:	builder_test.go:103
        	Error:      	Should NOT be empty, but was <nil>
        	Test:       	TestCredentialManifestBuilder
time="2022-07-04T10:42:40+05:30" level=error msg="credential application not valid against schema" error="credential_application.format: Invalid type. Expected: object, given: null"
time="2022-07-04T10:42:40+05:30" level=error msg="credential application not ready to be built" error="application failed json schema validation: credential_application.format: Invalid type. Expected: object, given: null"
time="2022-07-04T10:42:40+05:30" level=error msg="credential fulfillment not valid against schema" error="credential_fulfillment.descriptor_map: Invalid type. Expected: array, given: null"
time="2022-07-04T10:42:40+05:30" level=error msg="credential fulfillment not ready to be built" error="fulfillment failed json schema validation: credential_fulfillment.descriptor_map: Invalid type. Expected: array, given: null"
time="2022-07-04T10:42:43+05:30" level=error msg="credential manifest not valid against schema" error="Could not read schema from HTTP, response status is 404 Not Found"
--- FAIL: TestCredentialManifest (2.48s)
    --- FAIL: TestCredentialManifest/Credential_Manifest_Vector_1 (2.48s)
        model_test.go:37:
            	Error Trace:	model_test.go:37
            	Error:      	Received unexpected error:
            	            	Could not read schema from HTTP, response status is 404 Not Found
            	            	manifest failed json schema validation
            	            	github.com/TBD54566975/ssi-sdk/credential/manifest.(*CredentialManifest).IsValid
            	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/model.go:36
            	            	github.com/TBD54566975/ssi-sdk/credential/manifest.TestCredentialManifest.func1
            	            		/Users/akmb2/workspace/github.com/andorsk/ssi-sdk/credential/manifest/model_test.go:37
            	            	testing.tRunner
            	            		/usr/local/go/src/testing/testing.go:1439
            	            	runtime.goexit
            	            		/usr/local/go/src/runtime/asm_arm64.s:1263
            	Test:       	TestCredentialManifest/Credential_Manifest_Vector_1
--- FAIL: TestCredentialManifestSchemas (1.97s)
    schema_test.go:17:
        	Error Trace:	schema_test.go:17
        	Error:      	Received unexpected error:
        	            	Could not read schema from HTTP, response status is 404 Not Found
        	Test:       	TestCredentialManifestSchemas
FAIL
FAIL	github.com/TBD54566975/ssi-sdk/credential/manifest	7.632s```

[andorsk]

I've raised an issue regarding the build failing here: #132