Bump actions/checkout from 4 to 6 (#52)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
       NINJA_STATUS: "[Built edge %f of %t in %e sec] "
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0  # such that setuptools_scm can do its job correctly
 

.github/workflows/publish.yml

@@ -22,7 +22,7 @@ jobs:
     name: Build source distribution
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0  # such that setuptools_scm can do its job correctly
 
@@ -40,7 +40,7 @@ jobs:
     outputs:
       include: ${{ steps.set-matrix.outputs.include }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install cibuildwheel
         run: pipx install cibuildwheel==2.19.2
       - id: set-matrix
@@ -77,7 +77,7 @@ jobs:
         include: ${{ fromJson(needs.generate-wheels-matrix.outputs.include) }}
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0  # such that setuptools_scm can do its job correctly