change pod mutator webhook to fail-open

[M00nF1sh]

Issue

<n/a>

Description

Change the pod mutator webhook's failurePolicy from Fail to Ignore, thus it became fail-open.

The pod mutator's purpose is to inject a readinessGate thus during a deployment, old pods will be kept alive until new pods registered and became healthy in targetGroups.
Currently the failurePolicy is fail, so under extreme cases where the controller itself is not alive, this could delay the cluster from recovery by preventing critical pods from been created.
Given the podReadinessGate feature don't have impact on the pod's functionality itself, switch failPolicy to "Ignore" make more sense.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• [] Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[oliviassss]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: M00nF1sh, oliviassss

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