Remove support for Python 3.8

[stefanor]

Thanks for contributing, make sure you address all the checklists (for details on how see development documentation)

• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[gaborbernat]

Thank you for your pull request — we really appreciate your contribution!
At this time, we are unable to drop support for Python 3.8. As part of our support policy, we have committed to maintaining compatibility for 18 months past Python 3.8’s official end-of-life, which extends until Tuesday, April 7, 2026.
Once that date has passed, we will be able to revisit changes that remove 3.8 support. We truly appreciate your understanding and look forward to future contributions!