🔧 Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -11,7 +11,7 @@ jobs:
     name: Lint
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
     - name: Set up Python 3.8
       uses: actions/setup-python@v5
       with:
@@ -37,7 +37,7 @@ jobs:
             python-version: "3.8"
             sphinx-version: "6.0"
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Set Up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v5
         with:
@@ -79,7 +79,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout source
-      uses: actions/checkout@v4
+      uses: actions/checkout@v5
     - name: Set up Python 3.10
       uses: actions/setup-python@v5
       with: