DOC: np.bool -> np.bool_
xref #34848, #34835

a couple missed that are causing doc build failures with numpy-1.20.0rc2, https://github.com/pandas-dev/pandas/pull/36092/checks?check_run_id=1662818738

probably want to backport this to prevent possible future ci failures
should we have a checker rule to prohibit? > should we have a checker rule to prohibit?

possible, i used `np.bool[^_]` but that misses

```
pandas/tests/io/excel/test_writers.py:    @pytest.mark.parametrize("np_type", [np.bool8, np.bool_])
pandas/tests/io/excel/test_writers.py:        # Test np.bool values read come back as float.
```
could change the comment as well and use `np.bool[^_8]` @simonjayhawkins you *may* have to remove the rule for backport but we shall see @meeseeksdev backport 1.2.x Something went wrong ... Please have  a look at my logs.