CompatHelper: bump compat for DocStringExtensions to 0.9, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the DocStringExtensions package from 0.8 to 0.8, 0.9. 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.

[jd-lara]

@iblis17 is it possible to merge this PR? it is preventing us from upgrading in several packages.

[jd-lara]

bump to @iblis17 to merge this please

[iblislin]

👌

[jd-lara]

Thanks!