Removed graphviz from poetry requirements and added to environment dependencies

[JetteThiele]

Fixes #
Graphviz wasn't installed on Windows via poetry
Therefore removed from poetry and added to environment dependencies

Before merging into dev-branch, please make sure that the following points are checked:

• All pre-commit tests passed locally with: pre-commit run -a
• File CHANGELOG.md was updated
• The docs were updated
  • if dataset.mds were updated, the dataset docs were regenerated using
    python docs/generate_dataset_mds.py

If packages were modified:

• File poetry.lock was updated with: poetry lock
• A new env was successfully set up

WARNING: When modifying use snakemake <=7.32.0, cf. #186

If data flow was adjusted:

• Data pipeline run finished successfully with: snakemake -jX

• Esys appdata was created successfully with: snakemake -jX make_esys_appdata

  (with X = desired number of cores, e.g. 1)