Fix deploy keys API annotation

lib/api/deploy_keys.rb

@@ -161,9 +161,7 @@ def find_by_deploy_key(project, key_id)
         end
       end
 
-      desc 'Delete deploy key for a project' do
-        success Key
-      end
+      desc 'Delete deploy key for a project'
       params do
         requires :key_id, type: Integer, desc: 'The ID of the deploy key'
       end