See https://discourse.phabricator-community.org/t/storage-upgrade-error/3748.
It is broadly unsafe for migrations to use "save()". If the object gains new fields later, the query will include "SET newField = X", which will fail against the old schema which is in the process of being upgraded.
Instead, migrations must issue raw SQL against the schema as it is expected to exist at the time the migration executes.
Migrations have followed this rule for a long time, but this ~6 year old migration was overlooked. Update it to issue a raw query to perform the policy update.