UI: Fix proprty Undo not updating settings properly

Settings would not update properly because obs_source_update() can only
apply the settings value to the existing settings, so it could not
remove values. This change fully erases existing settings and replaces
it with the target settings instead.

UI/context-bar-controls.cpp

@@ -58,7 +58,7 @@ void SourceToolbar::SetUndoProperties(obs_source_t *source)
 		obs_data_t *settings = obs_data_create_from_json(data.c_str());
 		obs_source_t *source = obs_get_source_by_name(
 			obs_data_get_string(settings, "undo_sname"));
-		obs_source_update(source, settings);
+		obs_source_reset_settings(source, settings);
 
 		obs_source_t *scene_source =
 			obs_get_source_by_name(scene_name.c_str());

UI/window-basic-properties.cpp

@@ -368,7 +368,7 @@ void OBSBasicProperties::on_buttonBox_clicked(QAbstractButton *button)
 				obs_data_create_from_json(data.c_str());
 			obs_source_t *source = obs_get_source_by_name(
 				obs_data_get_string(settings, "undo_sname"));
-			obs_source_update(source, settings);
+			obs_source_reset_settings(source, settings);
 
 			obs_source_update_properties(source);