Drop no-longer-needed custom changes to /usr/bin/pip*
    
    pip >= 20 has a mechanism that replaces our pip-allow-different-versions.patch
    However, we kept our patch to support users doing e.g.:
    
        $ pip install --user --upgrade 'pip<20'
    
    However, pip 19.3.1 (the latest <20 version) does not even operate without distutils:
    
        (venv3.12)$ pip list
        Package    Version
        ---------- -------
        pip        22.3.1
        setuptools 65.5.0
    
        (venv3.12)$ pip install --upgrade 'pip<20'
        ...
    
        (venv3.12) $ pip list
        Traceback (most recent call last):
          File ".../venv3.12/bin/pip", line 5, in <module>
            from pip._internal.main import main
          File ".../venv3.12/lib64/python3.12/site-packages/pip/_internal/main.py", line 13, in <module>
            from pip._internal.cli.autocompletion import autocomplete
          File ".../venv3.12/lib64/python3.12/site-packages/pip/_internal/cli/autocompletion.py", line 11, in <module>
            from pip._internal.cli.main_parser import create_main_parser
          File ".../venv3.12/lib64/python3.12/site-packages/pip/_internal/cli/main_parser.py", line 7, in <module>
            from pip._internal.cli import cmdoptions
          File ".../venv3.12/lib64/python3.12/site-packages/pip/_internal/cli/cmdoptions.py", line 19, in <module>
            from distutils.util import strtobool
        ModuleNotFoundError: No module named 'distutils'
    
    Hence, it no longer makes any sense to keep the patch with Python 3.12.