use latest python setup gh actions (#295)

* use latest python setup gh actions

* cache via setup.py

actions/setup-python#549

.github/workflows/run-tests.yml

@@ -12,18 +12,16 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Set up Python 3.9
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v4
       with:
-        python-version: 3.9
-    - uses: actions/cache@v2
-      with:
-        path: ${{ env.pythonLocation }}
-        key: ${{ env.pythonLocation }}-${{ hashFiles('setup.py') }}
+        python-version: '3.9'
+        cache: 'pip' # caching pip dependencies
+        cache-dependency-path: setup.py
     - name: Install dependencies
       run: |
         pip install -U pip
         pip install -U .[testing,docs]
     - name: Run tests
-      run: python -m unittest discover
+      run: python -m unittest discover