CLN: Remove cdate_range, raise_on_error keyword, categories and ordered keywords in astype
- [x] xref #6581
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Removed:

- `cdate_range`
- `raise_on_error` keyword in `.where` and `.mask`
- `ordered` and `categories` keywords in `.astype`
LGTM.