use _TS2 for findall

Author: MarcoGorelli

pandas-stubs/core/strings.pyi

@@ -166,7 +166,7 @@ class StringMethods(NoNewAttributesMixin, Generic[T, _TS, _TM, _TS2]):
     def count(self, pat: str, flags: int = ...) -> Series[int]: ...
     def startswith(self, pat: str | tuple[str, ...], na: Any = ...) -> Series[bool]: ...
     def endswith(self, pat: str | tuple[str, ...], na: Any = ...) -> Series[bool]: ...
-    def findall(self, pat: str, flags: int = ...) -> Series[list[str]]: ...
+    def findall(self, pat: str, flags: int = ...) -> _TS2: ...
     @overload
     def extract(
         self, pat: str, flags: int = ..., *, expand: Literal[True] = ...