STY: absolute imports in __init__ files
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I was just about to ping :) Thanks @MomIsBestFriend  Personally, I am -1 on those changes (or https://github.com/pandas-dev/pandas/pull/30827). 
@MomIsBestFriend before you do any more of such PRs on absolute imports (although I don't know if there are cases left?), can we first have a discussion about this? @jorisvandenbossche I actually did want to discuss this, so I opened [this PR](https://github.com/pandas-dev/pandas/pull/30822) which as you can see has only two changes. And when it got merged I saw it as an approval to go and change even more files.

Anyway, I don't mind reverting #30822, #30827, #30828.
Until this topic is fully discussed.