[3.10] gh-101144: Allow zipfile.Path .open & .read_text encoding to be positional...

[3.10] gh-101144: Allow zipfile.Path .open & .read_text encoding to be positional (GH-101179) (GH-101182)

The zipfile.Path open() and read_text() encoding parameter can be supplied as a positional argument without causing a TypeError again. 3.10.0b1 included a regression that made it keyword only.

Documentation update included as users writing code to be compatible with a wide range of versions will need to consider this for some time..

(cherry picked from commit 5927013e47a8c63b70e104152351f3447baa819c)
(cherry picked from commit efe3a389cabd7295e6e0938767cdc4055c871e3c)

Co-authored-by: Gregory P. Smith <greg@krypto.org> [Google]
Automerge-Triggered-By: GH:gpshead