Add missing extension to docs links

[danbarr]

Summary

The new rule evaluations page added in #4481 has three links to the secret_scanning rule page that are missing the .md extension. These worked in the minder-docs.stacklok.dev build but caused the Docusaurus build to fail on a broken link error for the cloud docs overlay.

Change Type

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

Confirmed links are working via local preview.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.