ci: Disable checking Python 3.6

Author: dbanty

.github/workflows/checks.yml

@@ -11,7 +11,7 @@ jobs:
   test:
     strategy:
       matrix:
-        python: [ 3.6, 3.7, 3.8, 3.9 ]
+        python: [ 3.7, 3.8, 3.9 ]
         os: [ ubuntu-latest, macos-latest, windows-latest ]
     runs-on: ${{ matrix.os }}