ci(deps): 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](https://github.com/actions/checkout/compare/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] <support@github.com>

.github/workflows/prchecks.yml

@@ -23,7 +23,7 @@ jobs:
       fail-fast: false
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: actions/setup-python@v6
       with:
         python-version: 3.x

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
         name: Build and release to PyPI
         runs-on: ubuntu-latest
         steps:
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
             - name: Set up Python
               uses: actions/setup-python@v6
               with:

.github/workflows/tests.yml

@@ -28,7 +28,7 @@ jobs:
 
     name: Python ${{ matrix.python_version }} (${{ matrix.os }})
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python_version }}
       uses: actions/setup-python@v6
       with:
@@ -62,7 +62,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Prepare Python
         uses: actions/setup-python@v6
         with: