Add missing configuration to enable the awsmachinetemplate validating webhook

[cnmcavoy]

What type of PR is this?
/kind bug

What this PR does / why we need it:
Enables the AWSMachineTemplate validating webhook. Unclear why it was not previously configured.

The CloudInit behavior was removed, as it was copied from the v1alpha4 resources in c09f55f8f2249d9fde6d7878a6595bf1c4672ff2 and kept being dragged forward, but the comment indicates it was only needed for one resource version upgrade, so I think it's no longer necessary.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #4116

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

Release note:

Fixed bug which resulted in the AWSMachineTemplate validating webhook not being enabled as expected.

[k8s-ci-robot]

Hi @cnmcavoy. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[Ankitasw]

/ok-to-test

[cnmcavoy]

/retest

[cnmcavoy]

/test pull-cluster-api-provider-aws-e2e
/test pull-cluster-api-provider-aws-e2e-eks

[cnmcavoy]

/test pull-cluster-api-provider-aws-e2e-eks

[Ankitasw]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Ankitasw

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