Grep in `release.sh` in Git Bash not working

[V3lop5]

Describe the bug
While running

version=$(grep -Po '(?<=__version__ = ")[^"]+' ./ensysmod/__init__.py)

the error grep: -P supports only unibyte and UTF-8 locales occurred.

To Reproduce
Steps to reproduce the behavior:

1. Checkout main branch
2. sh scripts/release.sh

Expected behavior
Grep should retrieve the current version from __init__.py.

Additional context
Full log:

Paul@D-Paule MINGW64 ~/Git/NOWUM/EnSysMod (main)
$ sh scripts/release.sh patch
OK: Running release script for a patch bump ...
OK: Currently on branch main.
OK: No uncommitted changes found.
grep: -P supports only unibyte and UTF-8 locales
OK: Current version:
OK: New version: 1
sed: -e expression #1, char 0: no previous regular expression