Adapt Phylogenetic Tree to count dataframe

[AgnesBaud]

Description

See #97

Changelogs

• adapt_phylogenetic_tree_to_counts_df function in utils/phylogenetic_tree_editing.py

Issue(s)

Fixes #97

Definition of Done

• [x] New code is tested with unit tests
• [ ] Documentation has been updated
• [ ] Pull Request has been revised by a maintainer of the project

[AgnesBaud]

Removing python 3.6 from python-package.yml because not supported by setup-python anymore:

"Python 3.6 reached end-of-life on Dec 12, 2021. Therefore, we won’t be supporting it with new versions of our hosted runners.(...)"