Fix block validation on WordPress 6.2

[priethor]

What

Fixes block validation failing on WordPress 6.2, allowing posts to publish despite validation errors in blocks.

Why

While working on #271 to make e2e tests compatible with WP 6.2, one test failed for a valid reason related to production code: togglePublishSidebar() was added in WordPress 6.3 and doesn't exist in 6.2. The error broke the promise chain before it could return hasError = true. This caused the validation to silently fail, allowing posts with invalid blocks to be published.

How

Checking if togglePublishSidebar exists before calling it:

• The function is only used for closing the publish panel; validation logic is unaffected
• When the method doesn't exist, we skip the panel close, but validation still works correctly

Testing Instructions

1. Set up an instance of WordPress 6.2
2. Create a post with a testimonial block, or any SCF block with required fields
3. Clear a required field and try to publish
4. Verify the post is NOT published, and an error notice appears

[github-actions]

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Core Committers: Use this line as a base for the props when committing in SVN:

Props priethor, cbravobernal.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 9.37%. Comparing base (342675c) to head (f2f82a2).
⚠️ Report is 1 commits behind head on trunk.

Additional details and impacted files

@@           Coverage Diff           @@
##             trunk    #272   +/-   ##
=======================================
  Coverage     9.37%   9.37%           
  Complexity    4288    4288           
=======================================
  Files          266     266           
  Lines        33159   33159           
=======================================
  Hits          3108    3108           
  Misses       30051   30051           

Flag	Coverage Δ
e2e	21.83% <ø> (ø)
phpunit	6.08% <ø> (ø)

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[cbravobernal]

LGTM. But maybe we should increase the minimum WP Version.