Closed
Description
We split date_histo intervals between calendar and fixed intervals in #33727. At the same time, we deprecated the older, unified interval parameter.
It's been deprecated since 7.2, so we should be good to remove from 8.0 in my opinion. There is a non-negligible amount of code to handle the old intervals and it'd be great to clean that up.
This issue is a placeholder so we don't forget to remove it as 8.0 grows nearer :)