Replace "below" with "above" in `frontend_test.md`

What does this MR do and why?

It replaces a link's text as described below with as described previously.

The anchor is pointing to a header above while the link says "as described below".

Screenshots or screen recordings

N/A

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.