fix workflow

Author: duttonw

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: '3.6'
+          python-version: '3.x'
       - name: Install requirements
         run: pip install flake8 pycodestyle
       - name: Check syntax