CI: mypy validation failing on master

[Dr-Irv]

Happening in multiple PRs, e.g., https://github.com/pandas-dev/pandas/pull/41203/checks?check_run_id=3181637542

pandas/core/reshape/tile.py:421: error: No overload variant of "searchsorted" of "ndarray" matches argument types "Any", "str"  [call-overload]
pandas/core/reshape/tile.py:421: note: Possible overload variants:
pandas/core/reshape/tile.py:421: note:     def searchsorted(self, v: Union[int, float, complex, str, bytes, generic], side: Union[Literal['left'], Literal['right']] = ..., sorter: Union[_SupportsArray[dtype[Union[bool_, integer[Any]]]], Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]], Sequence[Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]]], Sequence[Sequence[Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]]]], Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]]]]], int, Sequence[int], Sequence[Sequence[int]], Sequence[Sequence[Sequence[int]]], Sequence[Sequence[Sequence[Sequence[int]]]], None] = ...) -> signedinteger[Any]
pandas/core/reshape/tile.py:421: note:     def searchsorted(self, v: Union[Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]], Union[Union[_SupportsArray[dtype[Any]], Sequence[_SupportsArray[dtype[Any]]], Sequence[Sequence[_SupportsArray[dtype[Any]]]], Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]], Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]], Union[bool, int, float, complex, str, bytes, Sequence[Union[bool, int, float, complex, str, bytes]], Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]], Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]], Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]]]], side: Union[Literal['left'], Literal['right']] = ..., sorter: Union[_SupportsArray[dtype[Union[bool_, integer[Any]]]], Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]], Sequence[Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]]], Sequence[Sequence[Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]]]], Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Union[bool_, integer[Any]]]]]]]], int, Sequence[int], Sequence[Sequence[int]], Sequence[Sequence[Sequence[int]]], Sequence[Sequence[Sequence[Sequence[int]]]], None] = ...) -> ndarray[Any, dtype[signedinteger[Any]]]
pandas/core/groupby/groupby.py:2949: error: Incompatible types in assignment (expression has type "Union[ExtensionArray, ndarray[Any, Any]]", variable has type "ndarray[Any, Any]")  [assignment]
pandas/core/groupby/groupby.py:2984: error: Incompatible types in assignment (expression has type "Union[ExtensionArray, ndarray[Any, Any]]", target has type "ndarray[Any, Any]")  [assignment]

[simonjayhawkins]

I don't think the mypy issues are related to numpy. We started using numpy 1.21.1 on ci in #42614.

can you update the issue title. see #42742 (comment) for two of the failures. Not sure which PR introduced the other.