fix: Remove fail-fast: false from dev deployment matrix strategy

[Copilot]

Summary | Résumé

Removes fail-fast: false from the matrix deployment strategy in dev_branch_deploy_images.yaml. The workflow now uses the default fail-fast behavior, halting all parallel deployments on first failure instead of allowing partial deployments.

Related Issues | Cartes liées

• Addresses feedback from Xmas Code Freeze Workflow #4339: Xmas Code Freeze Workflow #4339 (comment)

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).

After merging this PR

• I have verified that the tests / deployment actions succeeded
• I have verified that the smoke tests still pass on production
• I have communicated the release in the #notify Slack channel

What happens when your PR merges?

• Prefix the title of your PR:
  • fix: - tag main as a new patch release
  • feat: - tag main as a new minor release
  • BREAKING CHANGE: - tag main as a new major release
  • [MANIFEST] - tag main as a new patch release and deploy to production
  • chore: - use for changes to non-app code (ex: GitHub actions)
• Alternatively, change the VERSION file - this will not create a new tag, but rather will release the tag in VERSION to production.

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