Further reduce use of deprecated contextlib aliases (#6370)

stdlib/multiprocessing/synchronize.pyi

@@ -1,7 +1,8 @@
 import sys
 import threading
+from contextlib import AbstractContextManager
 from multiprocessing.context import BaseContext
-from typing import Any, Callable, ContextManager, Union
+from typing import Any, Callable, Union
 
 _LockLike = Union[Lock, RLock]
 
@@ -13,7 +14,7 @@ class Barrier(threading.Barrier):
 class BoundedSemaphore(Semaphore):
     def __init__(self, value: int = ..., *, ctx: BaseContext) -> None: ...
 
-class Condition(ContextManager[bool]):
+class Condition(AbstractContextManager[bool]):
     def __init__(self, lock: _LockLike | None = ..., *, ctx: BaseContext) -> None: ...
     if sys.version_info >= (3, 7):
         def notify(self, n: int = ...) -> None: ...
@@ -25,7 +26,7 @@ class Condition(ContextManager[bool]):
     def acquire(self, block: bool = ..., timeout: float | None = ...) -> bool: ...
     def release(self) -> None: ...
 
-class Event(ContextManager[bool]):
+class Event(AbstractContextManager[bool]):
     def __init__(self, lock: _LockLike | None = ..., *, ctx: BaseContext) -> None: ...
     def is_set(self) -> bool: ...
     def set(self) -> None: ...
@@ -42,6 +43,6 @@ class Semaphore(SemLock):
     def __init__(self, value: int = ..., *, ctx: BaseContext) -> None: ...
 
 # Not part of public API
-class SemLock(ContextManager[bool]):
+class SemLock(AbstractContextManager[bool]):
     def acquire(self, block: bool = ..., timeout: float | None = ...) -> bool: ...
     def release(self) -> None: ...