Adding Feature Category (pods) to some Decomposition Related Tests

As part of the new testing best practices: https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#feature-category-metadata

We will need to add pods as a feature category to a bunch of decomposition related specs:

1. (Done) Automatically locking new tables. Introduced here: !99287 (merged)
2. https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/lib/gitlab/database/migration_helpers/restrict_gitlab_schema_spec.rb
3. (Done) https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/tasks/gitlab/db/truncate_legacy_tables_rake_spec.rb
4. (Done) https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/tasks/gitlab/db/lock_writes_rake_spec.rb
5. https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/tasks/gitlab/db/decomposition/rollback/bump_ci_sequences_rake_spec.rb

Update: Some of them have been already updated as part of !106872 (merged). But we can go through the rest to make sure we have covered everything