MAINT: 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/constraints.yml

@@ -20,7 +20,7 @@ jobs:
     name: Update pip constraints
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version: "3.8"
@@ -40,7 +40,7 @@ jobs:
       github.event.pull_request.head.repo.full_name == github.repository
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ComPWA/update-pre-commit@main
 
   push:
@@ -50,7 +50,7 @@ jobs:
       - pip-constraints
       - pre-commit
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           token: ${{ secrets.PAT }}
       - uses: actions/download-artifact@v3

.github/workflows/notebook.yml

@@ -8,7 +8,7 @@ jobs:
     name: Run all notebooks
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@master
         with:
           python-version: "3.9"