CompatHelper: bump compat for Compat to 4, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Compat package from 2.1, 3 to 2.1, 3, 4.
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 #11 (e443458) into main (2fed970) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #11   +/-   ##
=======================================
  Coverage   94.02%   94.02%           
=======================================
  Files           6        6           
  Lines         201      201           
=======================================
  Hits          189      189           
  Misses         12       12           

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