RTC: Skip flaky stale-compaction test pending fix

[ramonjd]

What

Marks test_sync_stale_compaction_succeeds_when_newer_compaction_exists as skipped while the stale compaction handling fix is worked out separately.

Why

Noticed after #77980 was merged.

Tests_Collaboration_WpHttpPollingSyncServer::test_sync_stale_compaction_succeeds_when_newer_compaction_exists was failing.

The main reason, I think, is because WP_HTTP_Polling_Sync_Server is being loaded from Core now and collaboration.php skips it. Might need a dedicated Gutenberg_WP_HTTP_Polling_Sync_Server or something.

I tried a more meaningful fix in #77990 but I'd rather leave that to folks who have greater context.

Testing

CI should pass.

Use of AI

None.

[github-actions]

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[ramonjd]

closing in favour of #77986 - I didn't see it! 🤦🏻

[github-actions]

Flaky tests detected in f1c5dc0.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/25412628190
📝 Reported issues:

• [Flaky Test] Should insert content using the global inserter #77710 in /test/e2e/specs/widgets/editing-widgets.spec.js
• [Flaky Test] post title and content are editable and blocks can be inserted #77720 in /test/e2e/specs/editor/various/post-content-focus-mode.spec.js
• [Flaky Test] should show correct homepage actions based on current homepage or posts page #77385 in /test/e2e/specs/site-editor/homepage-settings.spec.js