BUG: DataFrameGroupBy.quantile raises for non-numeric dtypes rather than dropping columns
- [x] closes #27892
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Unlike what is mentioned in #27892, this will raise if there are no columns to aggregate. Both mean and median raise with "No numeric types to aggregate" in such a case, so I was thinking perhaps we should be consistent with them. Any thoughts @WillAyd and @TomAugspurger?

