fix(admission): change admissionWebhook.failurePolicy value to Ignore

[jrsmroz]

What this PR does / why we need it:

Which issue this PR fixes

kubernetes-ingress-controller/issues/2501

Special notes for your reviewer:

As suggested in kubernetes-ingress-controller/issues/2501 PR was tested manually:

Testing done:

1. Verified that unique constraint of secrets does trigger failure when admission failure policy is Ignore as described in kubernetes-ingress-controller/issues/2431. Verified that Fail policy prevents config from being applied
   
2. Verified that when controller is unreachable, the config is accepted if policy is Ignore.

• Installed kic with admission failure policy enabled, failure policy Ignore and faked the controller connectivity problem by setting CONTROLLER_ADMISSION_WEBHOOK_LISTEN to off in helm charts.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• PR is based off the current tip of the main branch.
• Changes are documented under the "Unreleased" header in CHANGELOG.md
• New or modified sections of values.yaml are documented in the README.md
• Commits follow the Kong commit message guidelines

[CLAassistant]

All committers have signed the CLA.

[pmalek]

You might want to fix the checkmarks in PR description 🙃