[collections] Add deque.__rmul__ (#16055)

Author: jason-scheffel

stdlib/collections/__init__.pyi

@@ -277,6 +277,7 @@ class deque(MutableSequence[_T]):
     def __iadd__(self, value: Iterable[_T], /) -> Self: ...
     def __add__(self, value: Self, /) -> Self: ...
     def __mul__(self, value: int, /) -> Self: ...
+    def __rmul__(self, value: int, /) -> Self: ...
     def __imul__(self, value: int, /) -> Self: ...
     def __lt__(self, value: deque[_T], /) -> bool: ...
     def __le__(self, value: deque[_T], /) -> bool: ...