remove SingleConstructorOffset.__reduce__ (#1342)

just remove `__reduce__`

Author: MarcoGorelli

pandas-stubs/_libs/tslibs/offsets.pyi

@@ -89,8 +89,7 @@ class BaseOffset:
     @property
     def nanos(self) -> int: ...
 
-class SingleConstructorOffset(BaseOffset):
-    def __reduce__(self): ...
+class SingleConstructorOffset(BaseOffset): ...
 
 class Tick(SingleConstructorOffset):
     def __init__(self, n: int = ..., normalize: bool = ...) -> None: ...