correct physics3d debug draw camera (#16927)

cocos/2d/CCScene.cpp

@@ -258,9 +258,14 @@ void Scene::render(Renderer* renderer, const Mat4* eyeTransforms, const Mat4* ey
             director->loadProjectionMatrix(physics3dDebugCamera->getViewProjectionMatrix(), i);
         }
         
+        _physics3dDebugCamera->apply();
+        _physics3dDebugCamera->clearBackground();
+
         _physics3DWorld->debugDraw(renderer);
         renderer->render();
         
+        _physics3dDebugCamera->restore();
+
         for (unsigned int i = 0; i < multiViewCount; ++i)
             director->popProjectionMatrix(i);
     }