CompatHelper: bump compat for "StatsBase" to "0.34"

[github-actions[bot]]

This pull request changes the compat entry for the StatsBase package from 0.32, 0.33 to 0.32, 0.33, 0.34.

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.

[ablaom]

This is probably an important one to push along since so many packages depend on it.

[ablaom]

Thanks ❤️