Turn Backfill Off For Operations::FeatureFlag Model IID

In !22175 (merged) we added an iid to the Operations::FeatureFlag model and backfilled it for existing rows.

We did this in %12.8. In %13.0 or later, we can change the parameters to has_internal_id from backfill: true, presence: false to presence: true.

https://gitlab.com/gitlab-org/gitlab/blob/8240d01a5abbce53924deb278568d9d031ed8970/ee/app/models/operations/feature_flag.rb#L11

Reference:

• https://docs.gitlab.com/omnibus/update/#mandatory-upgrade-paths-for-version-upgrades
• https://docs.gitlab.com/ee/policy/maintenance.html#upgrade-recommendations

Original issue that introduced the column and the backfill: #33137 (closed)