gh-98602: [typing docs] Use quotes for forward reference in TypeVarTuple example (#98605)

Author: Eclips4

Doc/library/typing.rst

@@ -1351,7 +1351,7 @@ These are not used in annotations. They are building blocks for creating generic
         Shape = TypeVarTuple('Shape')
         class Array(Generic[*Shape]):
             def __getitem__(self, key: tuple[*Shape]) -> float: ...
-            def __abs__(self) -> Array[*Shape]: ...
+            def __abs__(self) -> "Array[*Shape]": ...
             def get_shape(self) -> tuple[*Shape]: ...
 
     Type variable tuples can be happily combined with normal type variables::