Bump flutter version (#102)

Author: Ali Abdelfattah

pubspec.yaml

@@ -1,5 +1,5 @@
 name: instabug_flutter
-version: 8.7.0
+version: 9.0.0
 description: >-
   Instabug is an in-app feedback and bug reporting tool for mobile apps. 
   With just a simple shake, your users or beta testers can report bugs or