ci: remove flaky assertion from hook e2e test

[toyamagu-2021]

Almost same as #11384
Remove flaky assertion which causes nil pointer dereference.

Partial fix for #10807

=== PASS: HooksSuite/TestTemplateLevelHooksDagSuccessVersion
    suite.go:87: test panicked: runtime error: invalid memory address or nil pointer dereference
        goroutine 583 [running]:
        runtime/debug.Stack()
        	/opt/hostedtoolcache/go/1.21.1/x64/src/runtime/debug/stack.go:24 +0x5e
        github.com/stretchr/testify/suite.failOnPanic(0xc0006ba820, {0x1d5c7e0, 0x33ed890})
        	/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.8.4/suite/suite.go:87 +0x39
        github.com/stretchr/testify/suite.Run.func1.1()
        	/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.8.4/suite/suite.go:183 +0x24c
        panic({0x1d5c7e0?, 0x33ed890?})
        	/opt/hostedtoolcache/go/1.21.1/x64/src/runtime/panic.go:914 +0x21f
        github.com/argoproj/argo-workflows/v3/test/e2e.(*HooksSuite).TestTemplateLevelHooksDagSuccessVersion.func9(0xc0009d4fa8?, 0x21665e0?, 0x4?)
        	/home/runner/work/argo-workflows/argo-workflows/test/e2e/hooks_test.go:284 +0x13
        github.com/argoproj/argo-workflows/v3/test/e2e.(*HooksSuite).TestTemplateLevelHooksDagSuccessVersion.(*Then).ExpectWorkflowNode.func13(0x232de40?, 0xc00072[802](https://github.com/argoproj/argo-workflows/actions/runs/6440841701/job/17490095560?pr=11963#step:16:803)0, 0xc0009d54b8?)
        	/home/runner/work/argo-workflows/argo-workflows/test/e2e/fixtures/then.go:110 +0x379
        github.com/argoproj/argo-workflows/v3/test/e2e/fixtures.(*Then).expectWorkflow(0xc0009d5558, {0xc0008d3260, 0x1f}, 0xc0009d5538)
        	/home/runner/work/argo-workflows/argo-workflows/test/e2e/fixtures/then.go:68 +0x313
        github.com/argoproj/argo-workflows/v3/test/e2e/fixtures.(*Then).ExpectWorkflowNode(...)
        	/home/runner/work/argo-workflows/argo-workflows/test/e2e/fixtures/then.go:85
        github.com/argoproj/argo-workflows/v3/test/e2e.(*HooksSuite).TestTemplateLevelHooksDagSuccessVersion(0x0?)
        	/home/runner/work/argo-workflows/argo-workflows/test/e2e/hooks_test.go:281 +0x3f5
        reflect.Value.call({0xc000696cc0?, 0xc000641e48?, 0x2897babdc1?}, {0x2040c69, 0x4}, {0xc0000f1e70, 0x1, 0x1a9b0c8?})
        	/opt/hostedtoolcache/go/1.21.1/x64/src/reflect/value.go:596 +0xce7
        reflect.Value.Call({0xc000696cc0?, 0xc000641e48?, 0xc00068d500?}, {0xc0000f1e70?, 0x53056d?, 0x2db0ae0?})
        	/opt/hostedtoolcache/go/1.21.1/x64/src/reflect/value.go:380 +0xb9
        github.com/stretchr/testify/suite.Run.func1(0xc0006ba820)
        	/home/runner/go/pkg/mod/github.com/stretchr/testify@v1.8.4/suite/suite.go:197 +0x467
        testing.tRunner(0xc0006ba820, 0xc00078def0)
        	/opt/hostedtoolcache/go/1.21.1/x64/src/testing/testing.go:1595 +0xff
        created by testing.(*T).Run in goroutine 527
        	/opt/hostedtoolcache/go/1.21.1/x64/src/testing/testing.go:1648 +0x3ad
=== SLOW TEST:  HooksSuite/TestTemplateLevelHooksDagFailVersion took 20s
=== SLOW TEST:  HooksSuite/TestTemplateLevelHooksDagHasDependencyVersion took 17s
=== SLOW TEST:  HooksSuite/TestTemplateLevelHooksDagSuccessVersion took 44s
=== NAME  TestHooksSuite
    e2e_suite.go:86: to learn how to diagnose failed tests: https://argoproj.github.io/argo-workflows/running-locally/#running-e2e-tests-locally
--- FAIL: TestHooksSuite (83.10s)
    --- PASS: TestHooksSuite/TestTemplateLevelHooksDagFailVersion (21.07s)
    --- PASS: TestHooksSuite/TestTemplateLevelHooksDagHasDependencyVersion (17.43s)
    --- FAIL: TestHooksSuite/TestTemplateLevelHooksDagSuccessVersion (44.59s)