Use PEP 585 syntax wherever possible (#6717)

stdlib/graphlib.pyi

@@ -1,5 +1,5 @@
 from _typeshed import SupportsItems
-from typing import Generic, Iterable, Tuple, TypeVar
+from typing import Generic, Iterable, TypeVar
 
 _T = TypeVar("_T")
 
@@ -10,7 +10,7 @@ class TopologicalSorter(Generic[_T]):
     def is_active(self) -> bool: ...
     def __bool__(self) -> bool: ...
     def done(self, *nodes: _T) -> None: ...
-    def get_ready(self) -> Tuple[_T, ...]: ...
+    def get_ready(self) -> tuple[_T, ...]: ...
     def static_order(self) -> Iterable[_T]: ...
 
 class CycleError(ValueError): ...