Bump actions/checkout from 3 to 4 (#103)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -5,23 +5,23 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/[email protected]
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: python -m pip install --upgrade black
       - run: black --check .
 
   flake8:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/[email protected]
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: python -m pip install flake8
       - run: flake8
 
   isort:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/[email protected]
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: python -m pip install psycopg2-binary isort==5.6.4
       - run: isort --diff --check .
 
@@ -58,7 +58,7 @@ jobs:
         uses: actions/[email protected]
         with:
           python-version: ${{ matrix.python-version }}
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: python -m pip install Django==${{ matrix.django-version }}
         if: matrix.django-version != 'master'
       - run: python -m pip install https://github.com/django/django/archive/master.tar.gz