Clearing history increments version, else it does not generate an asterisk on modification if the scene was just saved. Fixes #18027.

Still I feel this line was commented for a reason. If you bisect a bug and find
this commit, let me know.

core/undo_redo.cpp

@@ -333,7 +333,7 @@ void UndoRedo::clear_history() {
 	while (actions.size())
 		_pop_history_tail();
 
-	//version++;
+	version++;
 }
 
 String UndoRedo::get_current_action_name() const {