Update Installing.md (#3847)

Fix an imprecise path name, and fix a meaningful typo `No Run --> Now run`.

docs/docs/Installing.md

@@ -238,7 +238,7 @@ import java.util.List;
 
 ### 8 RNN and React Native version
 
-react-native-navigation supports multiple React Native versions. Target the React Native version required by your project by specifying the RNN build flavor in `app/build.gradle`.
+react-native-navigation supports multiple React Native versions. Target the React Native version required by your project by specifying the RNN build flavor in `android/app/build.gradle`.
 
 ```diff
 android {