CompatHelper: bump compat for Arrow in [extras] to 2, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Arrow package from ~2.7.1 to ~2.7.1, 2.
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 84.30%. Comparing base (db085d2) to head (6819f03).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #399   +/-   ##
=======================================
  Coverage   84.30%   84.30%           
=======================================
  Files          23       23           
  Lines        3109     3109           
=======================================
  Hits         2621     2621           
  Misses        488      488           

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