CompatHelper: bump compat for DiagonalArrays in [weakdeps] to 0.3, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the DiagonalArrays package from 0.2.3 to 0.2.3, 0.3.
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 60.10%. Comparing base (94198b6) to head (bf4ecea).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #55   +/-   ##
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  Coverage   60.10%   60.10%           
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  Files           7        7           
  Lines         193      193           
=======================================
  Hits          116      116           
  Misses         77       77           

Flag	Coverage Δ
docs	22.91% <ø> (ø)

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