Upgrade/Install: Remove accidentally shipped RTC files on upgrade

[itzmekhokan]

Summary

• Adds real-time collaboration files to the $_old_files array in update-core.php so they are removed during core upgrades.
• Addresses #65325, where RTC files removed in [62334] were unintentionally included in the WordPress 7.0 release package due to a build server issue.
• The existing verify:old-files Grunt task will also fail builds if these files are present in the build/ directory, preventing recurrence.

Context

Real-time collaboration was removed from core in #65205 (62334, 62337, 62338 on the 7.0 branch). However, the files still shipped in wordpress-7.0.zip and the WordPress/WordPress 7.0 tag. The impact is mostly benign since the files are not loaded, but they should be cleaned up on upgrade and excluded from future builds.

Test plan

• Verify php -l src/wp-admin/includes/update-core.php passes
• Verify PHPCS reports no errors on the changed file
• Confirm build/wp-includes/collaboration/ does not exist locally
• Run npx grunt verify:old-files as part of a full build in CI
• Confirm upgrading from a 7.0.0 install with RTC files to 7.0.1 removes:
  • wp-includes/collaboration.php
  • wp-includes/collaboration/class-wp-http-polling-sync-server.php
  • wp-includes/collaboration/class-wp-sync-post-meta-storage.php
  • wp-includes/collaboration/interface-wp-sync-storage.php

Backport

This change should be backported to the 7.0 branch for the 7.0.1 milestone.

Trac ticket: https://core.trac.wordpress.org/ticket/65325

Use of AI Tools

N/A

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

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[masteradhoc]

Hey @itzmekhokan
Can you check the last comment by @johnbillion on core trac? https://core.trac.wordpress.org/ticket/65325#comment:4
We'd like to get this ready for WP 7.0.1 to be included if possible.

[itzmekhokan]

Hey @itzmekhokan Can you check the last comment by @johnbillion on core trac? https://core.trac.wordpress.org/ticket/65325#comment:4 We'd like to get this ready for WP 7.0.1 to be included if possible.

Hey @masteradhoc I've addressed the mentioned feedback.