doc: Better sec practice for PATs with private remote SAST configs

What does this MR do and why?

As discussed in slack we should show better security practices here than hard-coding the PAT into the CI configuration.

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.