CompatHelper: bump compat for KomaMRIPlots to 0.8, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the KomaMRIPlots package from 0.9 to 0.9, 0.8.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.52%. Comparing base (eb05128) to head (4c7afa6).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #425   +/-   ##
=======================================
  Coverage   90.52%   90.52%           
=======================================
  Files          51       51           
  Lines        2787     2787           
=======================================
  Hits         2523     2523           
  Misses        264      264           

Flag	Coverage Δ
core	90.37% <ø> (ø)

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