Performance Lab: Remove broken security advisory link from changelog

[wprashed]

Description

Fixes #2643.

The Performance Lab plugin readme.txt changelog entry for version 2.3.0 contained a link to a private GitHub security advisory (GHSA-66qq-69rw-6x63) which returns a 404 error when clicked from the WordPress.org plugin directory Development page.

This PR removes the broken hyperlink while retaining the changelog description and advisory identifier.

Testing Instructions

1. Review plugins/performance-lab/readme.txt in the v2.3.0 section.
2. Confirm the entry displays Infrastructure: Resolve low-severity security advisory GHSA-66qq-69rw-6x63. without the broken 404 URL.

[github-actions]

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Co-authored-by: wprashed <wprashed@git.wordpress.org>
Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>
Co-authored-by: nikvalani96 <valani9099@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>

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[mukeshpanchal27]

Thanks @wprashed for the PR!

There is some discussion happening on the issue about publishing the documentation, so let's wait for that to be resolved. Once we've decided whether to publish the documentation or what the next steps should be, we'll update the PR accordingly.

[nikvalani96]

Thanks for the clarification and for submitting the pull request to remove the inaccessible security advisory link. I appreciate the quick review and fix! 🙌