Generally, we like to use foreign key associations to destroy dependent
records. Where this is possible, it's faster and uses fewer resources
than doing it in GitLab.

In 028db84c , the notes association was
converted from `dependent: :destroy` to using foreign keys. However,
when destroying a specific project with > 60K notes, we're experiencing
statement timeouts in the staging environment. Additionally, notes have
a deprecated `attachments` uploader that requires Ruby intervention to
avoid orphaning files on disk - there are at least some notes on
GitLab.com that still use this deprecated uploader.

Since 2017, we've introduced the BatchDestroyDependentAssociations
concern, which takes care of processing large numbers of dependent
records in batches. Re-introducing `dependent: :destroy` on notes will
automatically make use of this code.

Changelog: fixed