chore: handle Gateway cleanup errors

[pmalek]

What this PR does / why we need it:

This PR makes handling Gateway cleanup errors hide errors that users do not need to see, which in most cases will cause a requeue anyway.

For example:

Gateway.gateway.networking.k8s.io \"kong\" is invalid: metadata.finalizers: Forbidden: no new finalizers can be added if the object is being deleted, found new finalizers []string{\"gateway-operator.konghq.com/cleanup-network-policies\"}

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