CompatHelper: bump compat for BlockBandedMatrices to 0.13, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the BlockBandedMatrices package from 0.12 to 0.12, 0.13. 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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 62.89%. Comparing base (023b1a4) to head (723ac5c). Report is 9 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #650 +/- ## =========================================== - Coverage 75.20% 62.89% -12.32% =========================================== Files 79 79 Lines 8445 8405 -40 =========================================== - Hits 6351 5286 -1065 - Misses 2094 3119 +1025 ```

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