Use SNS for international phone numbers

[sastels]

Summary | Résumé

Pinpoint is having a problem sending to international phone numbers. This PR sends them with SNS instead.

Related Issues | Cartes liées

• https://app.zenhub.com/workspaces/notify-planning-core-6411dfb7c95fb80014e0cab0/issues/gh/cds-snc/notification-planning-core/370

Test instructions | Instructions pour tester la modification

Send a SMS to the UK BT Text number +4408456021111
SNS should be used to send (in the logs "AWS SNS request finished in...")

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.

[ben851]

LGTM