Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/run_test_suite.yml

@@ -78,7 +78,7 @@ jobs:
       FORMAT: ${{ matrix.format }}
     steps:
       - name: checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: setup Ruby
         # https://github.com/ruby/setup-ruby#versioning