Bump actions/checkout from 5 to 6 in the actions group (#21)

Bumps the actions group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `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
  dependency-group: actions
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/test_publish.yml

@@ -28,7 +28,7 @@ jobs:
       fail-fast: false
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v6
@@ -58,7 +58,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name == 'push' && (github.ref == 'refs/heads/stable' || startsWith(github.ref, 'refs/tags/v'))
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Set up Python
       uses: actions/setup-python@v6