win32: remove duplicate check in vlc_cond_signal()

The same test is done in the underlying vlc_cond_broadcast().

src/win32/thread.c

@@ -226,9 +226,6 @@ void vlc_cond_destroy (vlc_cond_t *p_condvar)
 
 void vlc_cond_signal (vlc_cond_t *p_condvar)
 {
-    if (!p_condvar->clock)
-        return;
-
     /* This is suboptimal but works. */
     vlc_cond_broadcast (p_condvar);
 }