Fix documentation about "Full protection option after initial push"

What does this MR do and why?

Contributes to #420805 (closed)

Problem

Documentation is not correct and misleading.

Solution

Adjust documentation to match reality.

Screenshots or screen recordings

Project configuration when "Full protection option after initial push" is enabled.

• Only maintainers can push or merge
• Maintainers cannot force push

Developer	Maintainer

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.