Fix upgrade path from 3.4.0 (#16465)

Fix upgrade path from 3.4.0 (#16465)

3.4.1 dropped account_stats.lock_version, but in a way breaking the usual
upgrade path by requiring services to be reloaded after the post-migrations.

Indeed, `self.locking_column = nil` was not enough for Rails to ignore the
`lock_version` column when preparing statements on application load, resulting
in some ActiveRecord queries (typically those involving
`includes(:account_stat)`) erroring out with:

  ActiveRecord::StatementInvalid (PG::UndefinedColumn: ERROR:  column account_stats.lock_version does not exist