Remove unused indexes (#7829)

db/migrate/20180617162849_remove_unused_indexes.rb

@@ -0,0 +1,7 @@
+class RemoveUnusedIndexes < ActiveRecord::Migration[5.2]
+  def change
+    remove_index :statuses, name: "index_statuses_on_conversation_id"
+    remove_index :users, name: "index_users_on_filtered_languages"
+    remove_index :backups, name: "index_backups_on_user_id"
+  end
+end