Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

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

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

.github/workflows/ci.yml

@@ -47,7 +47,7 @@ jobs:
           - {VERSION: "3.9", TOXENV: "docs"}
     name: "${{ matrix.PYTHON.TOXENV }}${{ matrix.PYTHON.OS && format(' on {0}', matrix.PYTHON.OS) || '' }}"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Setup python
         uses: actions/setup-python@v4
         with:
@@ -71,7 +71,7 @@ jobs:
           - {CONTAINER: "ubuntu-rolling", TOXENV: "py311-cryptographyMain"}
     name: "${{ matrix.TEST.TOXENV }} on ${{ matrix.TEST.CONTAINER }}"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: /venv/bin/pip install tox
       - run: /venv/bin/tox -v
         env: