fix: conflict updating ControlPlane's finalizers is not an error

[pmalek]

What this PR does / why we need it:

This PR prevents the following error when e.g. creating a Gateway:

{"level":"error","ts":"2024-04-24T09:53:30Z","msg":"Reconciler error","controller":"controlplane","controllerGroup":"gateway-operator.konghq.com","controllerKind":"ControlPlane","ControlPlane":{"name":"gw1-42khv","namespace":"default"},"namespace":"default","name":"gw1-42khv","reconcileID":"ff149a0b-f471-4671-966c-37184e4224ee","error":"failed updating ControlPlane's finalizers : Operation cannot be fulfilled on controlplanes.gateway-operator.konghq.com \"gw1-42khv\": the object has been modified; please apply your changes to the latest version and try again","stacktrace":"sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler\n\t/home/runner/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:329\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem\n\t/home/runner/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:266\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2\n\t/home/runner/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:227"}

which is not an error which user should be aware of so just mask it and retry.

Which issue this PR fixes

Fixes #

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 significant changes

[czeslavo]

I think we could add a note the changelog for that.