Remove deprecated python version

Author: Petr Nechvátal

.github/workflows/pythonpackage.yml

@@ -9,7 +9,7 @@ jobs:
  strategy:
  max-parallel: 5
  matrix:
- python-version: [3.6, 3.7, 3.8, 3.9, "3.10", "3.11"]
+ python-version: [3.7, 3.8, 3.9, "3.10", "3.11"]
 
  steps:
  - uses: actions/checkout@v1