CompatHelper: bump compat for GraphPlot to 0.5, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the GraphPlot package from 0.3, 0.4 to 0.3, 0.4, 0.5.
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

Merging #868 (e8fc3b2) into master (88a8da0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #868   +/-   ##
=======================================
  Coverage   84.34%   84.34%           
=======================================
  Files          40       40           
  Lines        3794     3794           
=======================================
  Hits         3200     3200           
  Misses        594      594           

Flag	Coverage Δ
unittests	84.34% <ø> (ø)

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