DEPR: is_bool_dtype special-casing Index[object_all_bools]
- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

I'm pretty sure this is a leftover kludge from before we supported bool dtype Indexes.
```
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- hook id: sort-whatsnew-items
- duration: 0.05s
- exit code: 1
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diff --git a/doc/source/whatsnew/v2.1.0.rst b/doc/source/whatsnew/v2.1.0.rst
index db8e683..841419a 100644
--- a/doc/source/whatsnew/v2.1.0.rst
+++ b/doc/source/whatsnew/v2.1.0.rst
@@ -232,10 +232,10 @@ Deprecations
 - Deprecated parameter ``convert_type`` in :meth:`Series.apply` (:issue:`52140`)
 - Deprecated passing a dictionary to :meth:`.SeriesGroupBy.agg`; pass a list of aggregations instead (:issue:`50684`)
 - Deprecated the "fastpath" keyword in :class:`Categorical` constructor, use :meth:`Categorical.from_codes` instead (:issue:`20110`)
+- Deprecated the behavior of :func:`is_bool_dtype` returning ``True`` for object-dtype :class:`Index` of bool objects (:issue:`52680`)
 - Deprecated the methods :meth:`Series.bool` and :meth:`DataFrame.bool` (:issue:`51749`)
 - Deprecated unused "closed" and "normalize" keywords in the :class:`DatetimeIndex` constructor (:issue:`52628`)
 - Deprecated unused "closed" keyword in the :class:`TimedeltaIndex` constructor (:issue:`52628`)
-- Deprecated the behavior of :func:`is_bool_dtype` returning ``True`` for object-dtype :class:`Index` of bool objects (:issue:`52680`)
``` updated+green Thanks @jbrockmendel 