Update pandas-stubs/core/strings.pyi

Co-authored-by: Irv Lustig <[email protected]>

Author: loicdiridollou

pandas-stubs/core/strings.pyi

@@ -46,7 +46,7 @@ _T_STR = TypeVar("_T_STR", bound=Series[str] | Index[str])
 # Used for the result of str.partition
 _T_OBJECT = TypeVar("_T_OBJECT", bound=Series[type[object]] | Index[type[object]])
 
-_slice = slice
+_slice: TypeAlias = slice
 
 class StringMethods(
     NoNewAttributesMixin,