CompatHelper: bump compat for Documenter to 1 for package test, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Documenter package from 0.25, 0.26, 0.27 to 0.25, 0.26, 0.27, 1 for package test.
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 90.88%. Comparing base (2a6e5e9) to head (7e9f40b).

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #524       +/-   ##
===========================================
+ Coverage    0.42%   90.88%   +90.46%     
===========================================
  Files          52       52               
  Lines        1423     1459       +36     
===========================================
+ Hits            6     1326     +1320     
+ Misses       1417      133     -1284     

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