conformance: fix GatewayInvalidRouteKind gateway API conformance test

[mlavacca]

What this PR does / why we need it:

The conformance test GatewayInvalidRouteKind is enabled again

Which issue this PR fixes:

Fixes #3228
Part of #3305

Special notes for your reviewer:

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

- [ ] the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Base: 72.2% // Head: 72.1% // Decreases project coverage by -0.1% ⚠️

Coverage data is based on head (ac2e84e) compared to base (f196d26).
Patch coverage: 87.3% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3513     +/-   ##
=======================================
- Coverage   72.2%   72.1%   -0.1%     
=======================================
  Files        126     126             
  Lines      14546   14554      +8     
=======================================
- Hits       10507   10503      -4     
- Misses      3376    3386     +10     
- Partials     663     665      +2     

Impacted Files	Coverage Δ
internal/controllers/gateway/gateway_utils.go	89.9% <87.3%> (-0.1%)	⬇️
...nternal/controllers/gateway/tlsroute_controller.go	73.4% <0.0%> (-2.4%)	⬇️
...ternal/controllers/gateway/httproute_controller.go	69.7% <0.0%> (-1.9%)	⬇️
internal/dataplane/kongstate/service.go	66.0% <0.0%> (-1.3%)	⬇️
...nternal/controllers/gateway/tcproute_controller.go	72.0% <0.0%> (+2.0%)	⬆️

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