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

[github-actions]

This pull request changes the compat entry for the AbstractGPs package from 0.4 to 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-commenter]

Codecov Report

Merging #214 (4a99aa0) into master (6818fe4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #214   +/-   ##
=======================================
  Coverage   86.42%   86.42%           
=======================================
  Files          17       17           
  Lines         442      442           
=======================================
  Hits          382      382           
  Misses         60       60           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6818fe4...4a99aa0. Read the comment docs.