CompatHelper: bump compat for "AbstractPlotting" to "0.15"

[github-actions[bot]]

This pull request changes the compat entry for the AbstractPlotting package from ^0.10, 0.11 to ^0.10, 0.11, 0.15.

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.