DOC: clean v1.1.1 release notes
@TomAugspurger I don't think we need the subheaders for bugfixes in patch releases Looks good. Thanks @jorisvandenbossche I've also updated `Styler` link.

That should just leave and `CategoricalIndex.format()` as dysfunctional (will do final check after merging this before adding release date) 

https://pandas.pydata.org/docs/dev/whatsnew/v1.1.1.html

Could link to Index.format() instead and re-write note for context.