Do not use an exit statement in transactions

With ActiveRecord 7.x, transactions are now rolled back whenever they
return early. Previously, they were still committed. With `next`, the
transactions aren't rolled back. This is also what RuboCop suggests.

For details:
- https://github.com/rails/rails/issues/45017
- https://docs.rubocop.org/rubocop-rails/cops_rails.html#railstransactionexitstatement