build: fix Meson python3 module deprecation
Meson prints the following warning now:
DEPRECATION: Project targeting '>= 0.41.0' but tried to use feature deprecated since '0.48.0': python3 module
Let's switch to the "new" python module to fix that.
This requires new .path() method available since Meson 0.50.0 so we need to increase the requirements.