EA: Tighten signature on DatetimeArray._from_sequence
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

xref #33254

There are a few more steps to get DatetimeArray._from_sequence down to the ideal behavior, this is just trimming the signature down to what its supposed to be.

_from_sequence_not_strict could use a better name