patch backwards compatible pkg_resources, avoid deprecation warn

[owenclaxton-SMC]

As mentioned on this issue

Example of the warning:

/usr/bin/vcs:6: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
  from pkg_resources import load_entry_point

Example trigger:

$ python3 --version
Python 3.12.3
$ python3 vcstool/vcstool/commands/help.py 
/home/owen/vcstool/vcstool/commands/help.py:4: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
  from pkg_resources import load_entry_point
usage: vcs <command>

Most commands take directory arguments, recursively searching for repositories
...

[owenclaxton-SMC]

Ah - #242