fix: emit target_reached signal after updating state

(cherry picked from commit 3e186ae0437610dca2b266f62b204f2d7bd34ced)

scene/2d/navigation_agent_2d.cpp

@@ -481,8 +481,8 @@ void NavigationAgent2D::_request_repath() {
 void NavigationAgent2D::_check_distance_to_target() {
 	if (!target_reached) {
 		if (distance_to_target() < target_desired_distance) {
-			emit_signal("target_reached");
 			target_reached = true;
+			emit_signal("target_reached");
 		}
 	}
 }