build: fix python-version selection with actions

s/PYTHON\_VERSION/python-version

Refs: https://github.com/actions/setup-python
Refs: https://github.com/nodejs/node/pull/32609

PR-URL: https://github.com/nodejs/node/pull/33589


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>