change python versions in matrix

.github/workflows/main.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8, 3.9, 3.10]
+        python-version: [3.9, 3.10, 3.11]
     services:
       postgres:
         image: postgres