Fix jobs_cache_index migration class name

db/migrate/20171222183504_add_jobs_cache_index_to_project.rb

 # See http://doc.gitlab.com/ce/development/migration_style_guide.html
 # for more information on how to write migrations for GitLab.
 
-class AddCacheIndexToProject < ActiveRecord::Migration
+class AddJobsCacheIndexToProject < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
 
   # Set this constant to true if this migration requires downtime.