ci: remove testing on Python 3.6, since its EOL

Author: gnikit

.github/workflows/test.yml

@@ -39,7 +39,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11-dev"]
+        python: ["3.7", "3.8", "3.9", "3.10", "3.11-dev"]
 
     steps:
       - name: Checkout code