chore(deps): update actions/checkout action to v2 (#48)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

.github/workflows/django_on_diff_os.yml

@@ -18,7 +18,7 @@ jobs:
         python_version: [3.7, 3.8]
         os: [macos-latest, windows-latest, ubuntu-latest]
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python_version }}
       uses: actions/setup-python@v1
       with: