ci: update cron schedule expression with co-authors to enable notifications

[dlachaume]

Content

This PR includes an update to the Nightly Docker Builds workflow, adjusting the cron schedule to 2:30 UTC. This change creates a commit with co-authors, which should enable notifications for multiple users.

Pre-submit checklist

• Branch
  • [x] Commit sequence broadly makes sense
  • [x] Key commits have useful messages
• PR
  • [x] No clippy warnings in the CI
  • [x] Self-reviewed the diff
  • [x] Useful pull request description
  • [x] Reviewer requested

[github-actions[bot]]

Test Results

    4 files  ±0     51 suites  ±0   10m 33s ⏱️ +5s 1 418 tests ±0  1 418 ✅ ±0  0 💤 ±0  0 ❌ ±0  1 629 runs  ±0  1 629 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit f720e349. ± Comparison against base commit 3af8a57a.

:recycle: This comment has been updated with latest results.