PyO3 0.22.6

This release corrects the check for free-threaded Python introduced in PyO3 0.22.2 to prevent users accidentally installing PyO3 packages on Python 3.13t; PyO3 0.22 does not support free-threaded Python. (Stay tuned for the 0.23 release coming very soon!)

Thanks @minrk for the report and @davidhewitt for the fix!