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] <[email protected]>

.github/workflows/tests.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout source
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Set up Python 3.8
       uses: actions/[email protected]
       with:
@@ -61,7 +61,7 @@ jobs:
           cibw_skip: '*-win_amd64'
     steps:
     - name: Checkout source
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Enable MSVC 64bit
       uses: ilammy/msvc-dev-cmd@v1
       if: matrix.os == 'windows-latest' && matrix.cibw_skip == '*-win32'
@@ -122,7 +122,7 @@ jobs:
 
     steps:
     - name: Checkout source
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Download wheels and sdist
       uses: actions/download-artifact@v3