CompatHelper: bump compat for BlockDiagonals to 0.2, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the BlockDiagonals package from 0.1 to 0.1, 0.2.
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 88.72%. Comparing base (6696da4) to head (8197c56).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #326   +/-   ##
=======================================
  Coverage   88.72%   88.72%           
=======================================
  Files          16       16           
  Lines        1960     1960           
=======================================
  Hits         1739     1739           
  Misses        221      221           

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[blegat]

Superseeded by #325