Update capabilities.md for more clarity

[cccsss01]

What this PR does / why we need it:

Received feedback from a developer it was unclear what the message meant, adding the noun at the end of the 2nd sentence provides more clarity instead of carrying the context from the 1st sentence. 

Which issue(s) does this PR fix (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #
no issue

Do I really need to do this?

Special notes for your reviewer:

[apeabody]

Thanks for the contribution @cccsss01!

The documentation is automatically built from the actual template, so you would want to update it directly (https://github.com/open-policy-agent/gatekeeper-library/blob/master/src/pod-security-policy/capabilities/src.rego) and then follow the build process (https://github.com/open-policy-agent/gatekeeper-library/tree/master?tab=readme-ov-file#development).

[stale]

This issue/PR has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.