CLN/DOC: standardize wording on previous-removals
In the 1.0.0 whatsnew we currently have 3 variants of "Removed :foo:X"

```
- Removed the previously deprecated :meth:`X`
- Removed previously deprecated :meth:`X`
- Removed :meth:`X`
```

I think we should standardize on one of these (lest readers think the difference is meaningful).  I don't particularly care which, but for this PR went with the last one as it is the least verbose