Fix regex flags accidentally passed as count

[musicinmybrain]

The flags argument to re.sub() was accidentally passed positionally in the place of the count argument in tests/test_settings.py. Fix this by passing it as a keyword argument, which additionally fixes a DeprecationWarning in Python 3.13+ due to passing flags and/or count as positional arguments. See: https://docs.python.org/3.13/library/re.html#re.sub

[hramezani]

Thanks @musicinmybrain