Fix `macOS-arm64` architecture value from lowercase to uppercase in CI

[dlachaume]

Content

This PR includes a fix related to the merge of the PR #1752. Error: https://github.com/input-output-hk/mithril/actions/runs/9548794327/job/26317878165#step:8:10

Rename /package-macOS-arm64 to /package-macOS-ARM64 to match the actions/upload-artifact@v4 nomenclature.

Pre-submit checklist

• Branch
  • [ ] Tests are provided (if possible)
  • [ ] Crates versions are updated (if relevant)
  • [ ] CHANGELOG file is updated (if relevant)
  • [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
• Documentation
  • [ ] Update README file (if relevant)
  • [ ] Update documentation website (if relevant)
  • [ ] Add dev blog post (if relevant)

Issue(s)

Relates to #1751

[github-actions[bot]]

Test Results

    4 files  ±0     51 suites  ±0   8m 46s :stopwatch: +26s 1 069 tests ±0  1 069 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  1 217 runs  ±0  1 217 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit 5f6c1f28. ± Comparison against base commit 0d4e3624.