Remove empty string path param tests

Closes #300 

These are ignored by every single consumer of the verification server:
https://github.com/palantir/conjure-rust-runtime/blob/master/conjure-verification/ignored-test-cases.yml#L99-L104
https://github.com/palantir/conjure-java-runtime/blob/develop/conjure-java-client-verifier/src/test/resources/ignored-test-cases.retrofit.yml#L123-L127
https://github.com/palantir/conjure-java-runtime/blob/develop/conjure-java-client-verifier/src/test/resources/ignored-test-cases.jersey.yml#L86-L90
https://github.com/palantir/conjure-typescript-runtime/blob/b1005c04a051fc44907d45e2e0e96c49b1427702/packages/conjure-client/src/__integTest__/tests.ts#L34-L35
https://github.com/palantir/conjure-go/blob/develop/conjure-go-verifier/ignored-test-cases.yml#L108-L111
https://github.com/palantir/conjure-python/blob/develop/conjure-python-verifier/resources/ignored_test_cases.yml#L118-L122

master-test-cases.yml

@@ -788,15 +788,13 @@ singlePathParam:
     - '9007199254740991'
 - type: string
   positive:
-    - '""'
     - '"hello"'
 - type: uuid
   positive:
     - '"d6ddc1ac-3c1b-11e8-b467-0ed5f89f718b"' # UUID v1
     - '"80e6dd13-5f42-4e33-ad18-f73875540c8b"' # UUID v4
 - type: AliasString
   positive:
-    - '""'
     - '"hello"'
 - type: EnumExample
   positive: