MAINT: cleanup for Python 3.9 as we have minimum requirement 3.10

`from __future__ import annotations  # only needed for Python ≤ 3.9` in report.py

While working on my PR, I just saw this, as we have a clear minimum requirement of Python 3.10, I think we can clean this up. There may be more occurrences like this. I can dig into these if maintainers agree this should be done.

Thanks! Looking forward to the decision from maintainers.