Subscription resource API validation.

[n3wscott]

Fixes #4931

• Update schema based on schema tool output
• Validated the webhooks are as expected.

[knative-prow-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
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[codecov]

Codecov Report

Merging #5361 (862e1b2) into main (99470ef) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #5361   +/-   ##
=======================================
  Coverage   82.35%   82.35%           
=======================================
  Files         194      194           
  Lines        6002     6002           
=======================================
  Hits         4943     4943           
  Misses        737      737           
  Partials      322      322           

Impacted Files	Coverage Δ
pkg/apis/messaging/v1/subscription_types.go	66.66% <ø> (ø)

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[evankanderson]

/lgtm
/approve

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: evankanderson

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