Flutter version bump (#1988)

Author: abdallahshaban557

docs/src/pages/[platform]/getting-started/installation/dependencies.flutter.mdx

@@ -4,8 +4,8 @@ You will need to add dependencies for the `amplify_authenticator` to the `pubspe
 
 ```yaml
 dependencies:
-  amplify_flutter: ^0.4.0
-  amplify_auth_cognito: ^0.4.0
+  amplify_flutter: ^0.5.0
+  amplify_auth_cognito: ^0.5.0
   amplify_authenticator: ^0.1.0
 ```