pyparsing support discontinued for py3.8

[PaulaKramer]

There has been a new pyparsing release and they discontinued support for Python versions < 3.9. See here for more info: https://github.com/pyparsing/pyparsing/releases/tag/3.2.0. Therefore, the CI for Python 3.8 currently fails (https://github.com/volkamerlab/KinFragLib/actions/runs/11338684278/job/31532296005).

To fix this, we could pin the pyparsing version in the environment file or we could completely remove the CI workflow for Python 3.8 and only include 3.9, since Python 3.8 reached end-of-life last week (see here: https://devguide.python.org/versions/).