Remove CI for unsupported python versions, add for 3.11 and 3.12

Author: jsspencer

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.11, 3.12]
 
     steps:
       - uses: actions/checkout@v2