Fix migration spec leaking state

What does this MR do and why?

Migrations that delete default records in the DB should be wrapped in a transaction so that succeeding specs are not affected.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

bin/rspec spec/migrations/add_work_items_related_link_restrictions_spec.rb spec/migrations/20240627231742_update_weight_widget_definitions_spec.rb

bin/rspec spec/migrations/add_work_items_related_link_restrictions_spec.rb spec/migrations/20240327214545_add_development_widget_to_work_item_types_spec.rb

Related to #471720