Update version to 7.0.0 in pubspec.yaml

Author: aaqibismail

packages/firebase_database/pubspec.yaml

@@ -2,7 +2,7 @@ name: firebase_database
 description: Flutter plugin for Firebase Database, a cloud-hosted NoSQL database
   with realtime data syncing across Android and iOS clients, and offline access.
 homepage: https://github.com/FirebaseExtended/flutterfire/tree/master/packages/firebase_database
-version: 6.1.0
+version: 7.0.0
 
 environment:
   sdk: ">=2.12.0-0 <3.0.0"