GitHub Actions enhancements (#289)

* GitHub Actions: Use built-in caching provided by setup-python

* GitHub Actions: add python 3.11 to testing matrix

.github/workflows/django.yml

@@ -7,24 +7,15 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.7, 3.8, 3.9, "3.10"]
+        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
 
     steps:
     - uses: actions/checkout@v3
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
-
-    - name: Cache pip
-      uses: actions/cache@v2
-      with:
-        path: ~/.cache/pip
-        key: ${{ runner.os }}-pip-${{ matrix.python-version }}-{{ hashFiles('requirements.txt') }}
-        restore-keys: |
-          ${{ runner.os }}-pip-${{ matrix.python-version }}
-          ${{ runner.os }}-pip-
-          ${{ runner.os }}-
+        cache: 'pip'
 
     - name: Install dependencies
       run: |