Change process type values to be consistent

[whabanks]

Summary | Résumé

Quick PR to fix the sms/email process type values for the default categories. Rather than high, normal, low, we'll use priority, normal, bulk for consistency sake.

Related Issues | Cartes liées

• Initial TemplateCategory client notification-admin#1884

Test instructions | Instructions pour tester la modification

1. Run the migration
2. Check your local DB
3. Note that the values for sms/email_process_type in the default categories are priority, normal, bulk.

Release Instructions | Instructions pour le déploiement

None.

Reviewer checklist | Liste de vérification du réviseur

• This PR does not break existing functionality.
• This PR does not violate GCNotify's privacy policies.
• This PR does not raise new security concerns. Refer to our GC Notify Risk Register document on our Google drive.
• This PR does not significantly alter performance.
• Additional required documentation resulting of these changes is covered (such as the README, setup instructions, a related ADR or the technical documentation).

⚠ If boxes cannot be checked off before merging the PR, they should be moved to the "Release Instructions" section with appropriate steps required to verify before release. For example, changes to celery code may require tests on staging to verify that performance has not been affected.

[jzbahrai]

you can't change a migration once it has been run, you have to add a new migration.

[whabanks]

Closing because we need a new migration file not an edit.