ci(dependabot): 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/ci.yml

@@ -13,7 +13,7 @@ jobs:
   check-manifest:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: pipx run check-manifest
 
   test:
@@ -39,7 +39,7 @@ jobs:
         with:
           access_token: ${{ github.token }}
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: tlambert03/setup-qt-libs@v1
 
@@ -66,7 +66,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Python
         uses: actions/setup-python@v4