Investigate and fix failures in webhook integration tests: `TestAdmissionWebhook_HTTPRoute`

[pmalek]

Problem statement

We have migrated webhook tests in #3141 to KO's integration test suite. 2 of the test cases there seem to be failing in CI:

        	Error Trace:	/home/runner/work/kong-operator/kong-operator/test/integration/validatingwebhook/validating_httproute_test.go:239
        	Error:      	An error is expected but got nil.
        	Test:       	TestAdmissionWebhook_HTTPRoute/a_httproute_with_an_invalid_path_regex_fails_validation
...
    validating_httproute_test.go:239: 
        	Error Trace:	/home/runner/work/kong-operator/kong-operator/test/integration/validatingwebhook/validating_httproute_test.go:239
        	Error:      	An error is expected but got nil.
        	Test:       	TestAdmissionWebhook_HTTPRoute/a_httproute_with_an_invalid_header_regex_fails_validation

Example failing CI links:

• https://github.com/Kong/kong-operator/actions/runs/21665906349/job/62461334733#step:7:3474
• https://github.com/Kong/kong-operator/actions/runs/21645822487/job/62397488306#step:7:3522

This issue tracks the effort to investigate and fix these.

[tao12345666333]

Could you please paste some job links here?

[pmalek]

Could you please paste some job links here?

Update the description.

[tao12345666333]

I will take a look