docs(firebase_app_installations): Changed import statement in documentation. (#8275)

Author: ABDERRAHMANE-OUALI

docs/installations/usage.mdx

@@ -6,7 +6,7 @@ sidebar_label: Usage
 To start using the Firebase Installations package within your project, import it at the top of your project files:
 
 ```dart
-import 'package:flutterfire_installations/flutterfire_installations.dart';
+import 'package:firebase_app_installations/firebase_app_installations.dart';
 ```
 
 Before using Firebase Installations, you must first have ensured you have [initialized FlutterFire](../overview.mdx#initializing-flutterfire).