Fix diff not rendering properly (#3751)

The diff does not render properly on https://wix.github.io/react-native-navigation/v2/#/docs/Installing?id=you-can-use-react-native-navigation-o. I believe the proposed change should fix this.

docs/docs/Installing.md

@@ -357,3 +357,4 @@ import App from "./App";
 +    }
 +  });
 +});
+```