remove deprecated preserveUnknownFields field

[cmorinupgrade]

Changes

Remove deprecated preserveUnknownFields field.

Reference: aws/amazon-vpc-cni-k8s#3487

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Run make test lint before submitting a PR
• Includes tests (if functionality changed/added)
• Includes docs (if user facing)
• Commit messages follow commit message best practices

Release Notes

Chart: Remove deprecated `preserveUnknownFields` field.

[tekton-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
To complete the pull request process, please assign puneetpunamiya after the PR has been reviewed.
You can assign the PR to them by writing /assign @puneetpunamiya in a comment when ready.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[anithapriyanatarajan]

@cmorinupgrade - Thanks for the PR. A few requests:

1. Include base CRD updates: Please also remove the deprecated preserveUnknownFields: false field from the source CRD files in config/base/, config/kubernetes/base/, and config/openshift/base/ to keep them in sync with the Helm chart templates.
2. Please verify: Helm upgrades work correctly (upgrade from previous version with preserveUnknownFields: false to new version without it) and make apply deploys successfully with the updated CRDs.

NIT: Consider adding to the PR description that this removes a field deprecated in favor of the x-kubernetes-preserve-unknown-fields annotation in the schema (which we already use correctly).