Only use latest Python to run linting

Author: borntyping

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: "ubuntu-latest"
     strategy:
       matrix:
-        python-version: ["3.5", "3.6", "3.7", "3.8", "3.9"]
+        python-version: ["3.9"]
     steps:
       - uses: "actions/checkout@master"
       - name: "🐍 Set up Python ${{ matrix.python-version }}"