ci: bump actions/checkout from 4 to 6 (#6)

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

@@ -10,7 +10,7 @@ jobs:
       matrix:
         python: ['3.9', '3.10', '3.11', '3.12', '3.13']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '${{ matrix.python }}'

.github/workflows/docs.yml

@@ -17,7 +17,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with: { python-version: '3.12' }
       - run: pip install -e '.[docs]'

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
       contents: write
       id-token: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '3.12'

.github/workflows/spec-drift.yml

@@ -11,7 +11,7 @@ jobs:
       pull-requests: write
       issues: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: '3.12'