Always alias collections.abc.Set (#6712)

stdlib/concurrent/futures/thread.pyi

@@ -1,6 +1,6 @@
 import queue
 import sys
-from collections.abc import Iterable, Mapping, Set  # equivalent to typing.AbstractSet, not builtins.set
+from collections.abc import Iterable, Mapping, Set as AbstractSet
 from threading import Lock, Semaphore, Thread
 from typing import Any, Callable, Generic, Tuple, TypeVar
 from weakref import ref
@@ -46,7 +46,7 @@ if sys.version_info >= (3, 7):
 class ThreadPoolExecutor(Executor):
     _max_workers: int
     _idle_semaphore: Semaphore
-    _threads: Set[Thread]
+    _threads: AbstractSet[Thread]
     _broken: bool
     _shutdown: bool
     _shutdown_lock: Lock

stdlib/unittest/case.pyi

@@ -3,7 +3,7 @@ import logging
 import sys
 import unittest.result
 from _typeshed import Self
-from collections.abc import Set  # equivalent to typing.AbstractSet, not builtins.set
+from collections.abc import Set as AbstractSet
 from contextlib import AbstractContextManager
 from types import TracebackType
 from typing import (
@@ -201,7 +201,7 @@ class TestCase:
     ) -> None: ...
     def assertListEqual(self, list1: list[Any], list2: list[Any], msg: Any = ...) -> None: ...
     def assertTupleEqual(self, tuple1: Tuple[Any, ...], tuple2: Tuple[Any, ...], msg: Any = ...) -> None: ...
-    def assertSetEqual(self, set1: Set[object], set2: Set[object], msg: Any = ...) -> None: ...
+    def assertSetEqual(self, set1: AbstractSet[object], set2: AbstractSet[object], msg: Any = ...) -> None: ...
     def assertDictEqual(self, d1: Mapping[Any, object], d2: Mapping[Any, object], msg: Any = ...) -> None: ...
     def fail(self, msg: Any = ...) -> NoReturn: ...
     def countTestCases(self) -> int: ...