Chore: Update ruby version (#665)

.rubocop.yml

@@ -80,6 +80,10 @@ Rails/BulkChangeTable:
     - 'db/migrate/20170511134418_latlong.rb'
     - 'db/migrate/20191027054756_create_contact_inboxes.rb'
     - 'db/migrate/20191130164019_add_template_type_to_messages.rb'
+Rails/UniqueValidationWithoutIndex: 
+  Exclude:
+    - 'app/models/channel/twitter_profile.rb'
+    - 'app/models/webhook.rb'
 AllCops:
   Exclude:
     - 'bin/**/*'