Use union instead of overloads in dateutil (#13184)

Author: kbaikov

stubs/python-dateutil/dateutil/relativedelta.pyi

@@ -63,24 +63,16 @@ class relativedelta:
     @weeks.setter
     def weeks(self, value: int) -> None: ...
     def normalized(self) -> Self: ...
-    # TODO: use Union when mypy will handle it properly in overloaded operator
-    # methods (#2129, #1442, #1264 in mypy)
     @overload
-    def __add__(self, other: relativedelta) -> Self: ...
-    @overload
-    def __add__(self, other: timedelta) -> Self: ...
+    def __add__(self, other: timedelta | relativedelta) -> Self: ...
     @overload
     def __add__(self, other: _DateT) -> _DateT: ...
     @overload
-    def __radd__(self, other: relativedelta) -> Self: ...
-    @overload
-    def __radd__(self, other: timedelta) -> Self: ...
+    def __radd__(self, other: timedelta | relativedelta) -> Self: ...
     @overload
     def __radd__(self, other: _DateT) -> _DateT: ...
     @overload
-    def __rsub__(self, other: relativedelta) -> Self: ...
-    @overload
-    def __rsub__(self, other: timedelta) -> Self: ...
+    def __rsub__(self, other: timedelta | relativedelta) -> Self: ...
     @overload
     def __rsub__(self, other: _DateT) -> _DateT: ...
     def __sub__(self, other: relativedelta) -> Self: ...