Bump actions/checkout from 6 to 7 - #16

Branch main (06a9815) and #16 are queued together for merge.

Required conditions of queue rule default for merge:

• check-success = "check-macos-linux-nix"

Required conditions to stay in the queue:

• -closed [📌 queue requirement]
• -conflict [📌 queue requirement]
• -draft [📌 queue requirement]
• any of:
  • author = dependabot[bot]
  • author = gepetto-flake-updater[bot]
  • author = github-actions[bot]
  • author = mc-rtc-nixpkgs-flake-updater[bot]
  • author = pre-commit-ci[bot]
• any of: [📌 queue -> configuration change requirements]
  • -mergify-configuration-changed
  • check-success = Configuration changed
• any of: [🔀 queue conditions]
  • all of [📌 queue conditions of queue rule default]