obs-transitions: Halve stinger padding to 250ms

Triggering a new transition too soon after a
stinger would cause the wrong scene to be displayed

plugins/obs-transitions/transition-stinger.c

@@ -231,7 +231,7 @@ static void stinger_transition_start(void *data)
 		proc_handler_call(ph, "get_duration", &cd);
 		proc_handler_call(ph, "get_nb_frames", &cd);
 		s->duration_ns =
-			(uint64_t)calldata_int(&cd, "duration") + 500000000ULL;
+			(uint64_t)calldata_int(&cd, "duration") + 250000000ULL;
 		s->duration_frames = (uint64_t)calldata_int(&cd, "num_frames");
 
 		if (s->transition_point_is_frame)