image-source: Actually defer slideshow, not image source

The previous commit in this module meant to defer the properties update
of the slideshow source, not the image source.  Wrong file was modified.

plugins/image-source/image-source.c

@@ -230,8 +230,6 @@ static obs_properties_t *image_source_properties(void *data)
 
 	obs_properties_t *props = obs_properties_create();
 
-	obs_properties_set_flags(props, OBS_PROPERTIES_DEFER_UPDATE);
-
 	if (s && s->file && *s->file) {
 		const char *slash;
 

plugins/image-source/obs-slideshow.c

@@ -908,6 +908,8 @@ static obs_properties_t *ss_properties(void *data)
 
 	/* ----------------- */
 
+	obs_properties_set_flags(ppts, OBS_PROPERTIES_DEFER_UPDATE);
+
 	obs_get_video_info(&ovi);
 	cx = (int)ovi.base_width;
 	cy = (int)ovi.base_height;