Allow WordPress.org Update URI when slug matches plugin directory

[ernilambar]

Fixes #1287

Relaxes Plugin_Updater_Check so the Update URI header is not flagged when it matches the same URL patterns accepted by the plugin directory API: wordpress.org or w.org, /plugin(s)/…, and the path slug matches the plugin slug. Any other value still reports plugin_updater_detected.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: ernilambar <nilambar@git.wordpress.org>
Co-authored-by: davidperezgar <davidperez@git.wordpress.org>
Co-authored-by: dd32 <dd32@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.