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] <[email protected]>

Author: dependabot[bot]

.github/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
       FORCE_COLOR: 1
       PY_COLORS: 1
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Switch to using Python 3.11 by default
       uses: actions/setup-python@v5
       with:

.github/workflows/tox.yml

@@ -26,7 +26,7 @@ jobs:
       matrix:
         python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:
@@ -48,7 +48,7 @@ jobs:
       matrix:
         toxenv: [docs, packaging, py311]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python 3.11
       uses: actions/setup-python@v5
       with: