Fix custom synced commands not changing the AI game state

The old ai.synced_command function always set the AI-context game state to changed when executing such a command. This was inadvertently omitted when the implementation was changed to invoke_synced_command in fef953a4. While custom synced commands may or may not change the game state and the engine has no means of determining this correctly in all cases (meaning that neither behavior is technically wrong), the fact that the behavior was changed should be considered a bug. This commit changes it back to how it was before fef953a4.

src/game_events/action_wml.cpp

@@ -338,6 +338,7 @@ WML_HANDLER_FUNCTION(do_command,, cfg)
 			/*show*/ true,
 			/*error_handler*/ &on_replay_error
 		);
+		ai::manager::get_singleton().raise_gamestate_changed();
 	}
 }