gh-125058: update _thread docs regarding interruptibility of `lock.…

…acquire()` (#125141)

Doc/library/_thread.rst

@@ -219,9 +219,11 @@ In addition to these methods, lock objects can also be used via the
 * Calling :func:`sys.exit` or raising the :exc:`SystemExit` exception is
  equivalent to calling :func:`_thread.exit`.
 
-* It is not possible to interrupt the :meth:`~threading.Lock.acquire` method on
- a lock --- the :exc:`KeyboardInterrupt` exception will happen after the lock
- has been acquired.
+* It is platform-dependent whether the :meth:`~threading.Lock.acquire` method
+ on a lock can be interrupted (so that the :exc:`KeyboardInterrupt` exception
+ will happen immediately, rather than only after the lock has been acquired or
+ the operation has timed out). It can be interrupted on POSIX, but not on
+ Windows.
 
 * When the main thread exits, it is system defined whether the other threads
  survive. On most systems, they are killed without executing