docs(*): move enabling multidex to root

docs/firestore/enabling-multidex.md

@@ -1,33 +0,0 @@
----
-title: Enabling Multidex
-description: The Cloud Firestore SDK on Android can sometimes cause Dex errors, learn how to fix them.
----
-
-The Android Firebase Firestore SDK is a large library, and in some scenarios it may bump you over the
-65k method limit on the Android build system.
-
-If you have added Cloud Firestore as a dependency and your application build is now failing with the following error,
-you'll need to [enable multidex](https://developer.android.com/studio/build/multidex#mdex-gradle).
-
-`Execution failed for task ':app:mergeDexDebug'.`
-
-## Enabling Multidex
-
-Open the `/android/app/build.gradle` file. Under `dependencies` we need to add the module, and then enable it
-within out `defaultConfig`:
-
-```groovy
-android {
-    defaultConfig {
-        // ...
-        multiDexEnabled true
-    }
-    // ...
-}
-
-dependencies {
-  implementation 'com.android.support:multidex:1.0.3'
-}
-```
-
-Once added, rebuild your application: `npx react-native run-android`.

docs/firestore/usage/index.md

@@ -25,8 +25,8 @@ cd ios/ && pod install
 If you're using an older version of React Native without autolinking support, or wish to integrate into an existing project,
 you can follow the manual installation steps for [iOS](/firestore/usage/installation/ios) and [Android](firestore/usage/installation/android).
 
-In some scenarios, your Android build may fail with the `app:mergeDexDebug` error. This required that multidex is enabled
-for your application. To learn more, read the [Enabling Multidex](/firestore/enabling-multidex) documentation.
+If you have started to receive a `app:mergeDexDebug` error after adding Cloud Firestore, please read the 
+[Enabling Multidex](/enabling-multidex) documentation for more information on how to resolve this error.
 
 # What does it do