Fix two migrations to satisfy the Migration/AddConcurrentIndex cop

db/migrate/20170207150212_add_indexes_to_mirrors.rb

@@ -5,8 +5,13 @@ class AddIndexesToMirrors < ActiveRecord::Migration
 
   disable_ddl_transaction!
 
-  def change
+  def up
     add_concurrent_index :projects, [:sync_time]
     add_concurrent_index :remote_mirrors, [:sync_time]
   end
+
+  def down
+    remove_index :projects, [:sync_time]
+    remove_index :remote_mirrors, [:sync_time]
+  end
 end

db/migrate/20170208144550_add_index_to_mirrors_last_update_at_fields.rb

@@ -5,8 +5,13 @@ class AddIndexToMirrorsLastUpdateAtFields < ActiveRecord::Migration
 
   disable_ddl_transaction!
 
-  def change
+  def up
     add_concurrent_index :projects, :mirror_last_successful_update_at
     add_concurrent_index :remote_mirrors, :last_successful_update_at
   end
+
+  def down
+    remove_index :projects, :mirror_last_successful_update_at
+    remove_index :remote_mirrors, :last_successful_update_at
+  end
 end