pyproject.toml: version_file requires setuptools_scm>=8

[wdconinc]

Description

When the switch was made from write_to to version_file, the version requirement on setuptools_scm was not increased. version_file is only available as of v8, https://github.com/pypa/setuptools-scm/blob/v8.0.4/CHANGELOG.md?plain=1#L62.

Tasks

Most tasks below are not applicable.

• run pre-commit on your machine
• run pytest on your machine
• Does this PR add new features and / or change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • update relevant docstrings and / or docs/ page
  • for any new features, add unit tests

[braingram]

Thanks for finding the mistake!