tests: fix feature gates used in TestDeployAllInOneDBLESSGateway

[pmalek]

What this PR does / why we need it:

TestDeployAllInOneDBLESSGateway performs an update and sets KIC's feature gates to testenv.GetFeatureGates() which by default include the KongServiceFacade=true

kubernetes-ingress-controller/test/consts/feature_gates.go

Lines 7 to 8 in 96941c3

	// user takes further action.
	DefaultFeatureGates = "GatewayAlpha=true,KongServiceFacade=true"

.

This is problematic because KongServiceFacade CRD is not installed by default and the controller which watches it doesn't have a fallback mechanism and just fails to start when the aforementioned CRD is missing

kubernetes-ingress-controller/internal/controllers/configuration/kongupstreampolicy_controller.go

Lines 155 to 164 in 30a2991

	if r.KongServiceFacadeEnabled {
	if err := mgr.GetCache().IndexField(
	context.Background(),
	&incubatorv1alpha1.KongServiceFacade{},
	upstreamPolicyIndexKey,
	indexServiceFacadesOnUpstreamPolicyAnnotation,
	); err != nil {
	return fmt.Errorf("failed to index KongServiceFacades on annotation %s: %w", kongv1beta1.KongUpstreamPolicyAnnotationKey, err)
	}
	}

This results in

2024-04-08T14:42:33.009629453Z stderr F Error: unable to create controller "*configuration.KongUpstreamPolicyReconciler": failed to index KongServiceFacades on annotation konghq.com/upstream-policy: no matches for kind "KongServiceFacade" in version "incubator.ingress-controller.konghq.com/v1alpha1"

This PR fixes that by setting the feature gates in the test to only enable the Gateway API alpha features.

[team-k8s-bot]

E2E (targeted) tests with KIND-based clusters were started at https://github.com/Kong/kubernetes-ingress-controller/actions/runs/8603061554

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.9%. Comparing base (6038c87) to head (6f0dbc5).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5832     +/-   ##
=======================================
+ Coverage   73.2%   73.9%   +0.6%     
=======================================
  Files        176     176             
  Lines      18194   18194             
=======================================
+ Hits       13332   13458    +126     
+ Misses      3882    3735    -147     
- Partials     980    1001     +21     

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[pmalek]

This seems to fix the issue.

The 2 failures in https://github.com/Kong/kubernetes-ingress-controller/actions/runs/8603061554/attempts/1 come from #5828