[3.12] gh-125058: update _thread docs regarding interruptibility of lock.acquire() (GH-125141) (#125307)

gh-125058: update `_thread` docs regarding interruptibility of `lock.acquire()` (GH-125141)
(cherry picked from commit 0135848)

Co-authored-by: Jan Kaliszewski <zuo@kaliszewski.net>

Author: miss-islington

Doc/library/_thread.rst

@@ -216,9 +216,11 @@ 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