remove unneeded use of AbstractContextManager from multiprocessing.synchronize (#12872)

stdlib/multiprocessing/synchronize.pyi

@@ -1,6 +1,5 @@
 import threading
 from collections.abc import Callable
-from contextlib import AbstractContextManager
 from multiprocessing.context import BaseContext
 from types import TracebackType
 from typing_extensions import TypeAlias
@@ -14,7 +13,7 @@ class Barrier(threading.Barrier):
         self, parties: int, action: Callable[[], object] | None = None, timeout: float | None = None, *ctx: BaseContext
     ) -> None: ...
 
-class Condition(AbstractContextManager[bool, None]):
+class Condition:
     def __init__(self, lock: _LockLike | None = None, *, ctx: BaseContext) -> None: ...
     def notify(self, n: int = 1) -> None: ...
     def notify_all(self) -> None: ...
@@ -22,6 +21,7 @@ class Condition(AbstractContextManager[bool, None]):
     def wait_for(self, predicate: Callable[[], bool], timeout: float | None = None) -> bool: ...
     def acquire(self, block: bool = ..., timeout: float | None = ...) -> bool: ...
     def release(self) -> None: ...
+    def __enter__(self) -> bool: ...
     def __exit__(
         self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None, /
     ) -> None: ...
@@ -34,9 +34,10 @@ class Event:
     def wait(self, timeout: float | None = None) -> bool: ...
 
 # Not part of public API
-class SemLock(AbstractContextManager[bool, None]):
+class SemLock:
     def acquire(self, block: bool = ..., timeout: float | None = ...) -> bool: ...
     def release(self) -> None: ...
+    def __enter__(self) -> bool: ...
     def __exit__(
         self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None, /
     ) -> None: ...