update for Python >= 3.10

[orbeckst]

___________________ ERROR collecting tests/test_utilities.py ___________________
ImportError while importing test module '/home/runner/work/GromacsWrapper/GromacsWrapper/tests/test_utilities.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/share/miniconda/envs/test/lib/python3.10/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_utilities.py:12: in <module>
    from collections import Iterable
E   ImportError: cannot import name 'Iterable' from 'collections' (/usr/share/miniconda/envs/test/lib/python3.10/collections/__init__.py)

[orbeckst]

from six.moves.collections_abc import Iterable