Add missing URL to snippet feature flag yml
What does this MR do?
In a recent MR I introduced a new feature flag, but forgot to fill in the introduced_by
value for the new feature flag config YML, as described by https://docs.gitlab.com/ee/development/feature_flags/development.html#feature-flag-definition-and-validation
Although not required by our process, I think it's useful information to have, especially because the next steps are not scheduled during the next milestone or so.