gh-74953: Fix PyThread_acquire_lock_timed() code recomputing the timeout (GH-93941)

Set timeout, don't create a local variable with the same name.
(cherry picked from commit f64557f)

Co-authored-by: Victor Stinner <[email protected]>

Author: miss-islington

Python/thread_pthread.h

@@ -506,7 +506,7 @@ PyThread_acquire_lock_timed(PyThread_type_lock lock, PY_TIMEOUT_T microseconds,
 #ifndef HAVE_SEM_CLOCKWAIT
         if (timeout > 0) {
             /* wait interrupted by a signal (EINTR): recompute the timeout */
-            _PyTime_t timeout = _PyDeadline_Get(deadline);
+            timeout = _PyDeadline_Get(deadline);
             if (timeout < 0) {
                 status = ETIMEDOUT;
                 break;