docs: add a note of helm not updating CRDs in the upgrade section

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 65.56%. Comparing base (0017043) to head (78e03ef). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #4675 +/- ## ========================================== - Coverage 65.57% 65.56% -0.02% ========================================== Files 211 211 Lines 31952 31952 ========================================== - Hits 20952 20948 -4 - Misses 9757 9760 +3 - Partials 1243 1244 +1 ```

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[zirain]

should consider add a new helm chart called gateway-crds-helm?

[arkodg]

should consider add a new helm chart called gateway-crds-helm?

this being tracked with https://github.com/envoyproxy/gateway/issues/4001