check low-coverage files

[orbeckst]

I manually checked coverage with

pytest -n 4 -v --cov=alchemlyb --pyargs alchemlyb.tests

and found a few files with (relatively) low coverage:

--------- coverage: platform darwin, python 3.10.14-final-0 ----------
Name                                                                                                   Stmts   Miss Branch BrPart  Cover
-----------------------------------------------------------------------------------------------------------------------------------------
~/envs/alchemlyb310dev/lib/python3.10/site-packages/alchemlyb/tests/parsing/test_parquet.py              38      7      2      0    82%
~/envs/alchemlyb310dev/lib/python3.10/site-packages/alchemlyb/tests/test_version.py                       9      1      0      0    89%
~/envs/alchemlyb310dev/lib/python3.10/site-packages/alchemlyb/parsing/gomc.py                           105      1     54      7    95%
~/envs/alchemlyb310dev/lib/python3.10/site-packages/alchemlyb/parsing/__init__.py                        20      0      6      1    96%

There might be some easy wins there to increase coverage further or trim unused code.