RackAttack config file was renamed to 'rack_attack_new.rb' so it was
able to co-exists with the Omnibus settings (for more info see
https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/31246#note_215110463)

Since the Omnibus RackAttack settings were removed on 13.0, we can
rename this initializer back to its original name.

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/218291