patch 8.1.2313: debugging where a delay comes from is not easy

Problem:    Debugging where a delay comes from is not easy.
Solution:   Use different values when calling ui_delay().

src/if_xcmdsrv.c

@@ -556,7 +556,7 @@ ServerWait(
     time_t	    now;
     XEvent	    event;
 
-#define UI_MSEC_DELAY 50
+#define UI_MSEC_DELAY 53
 #define SEND_MSEC_POLL 500
 #ifndef HAVE_SELECT
     struct pollfd   fds;