Use Postgres 13 on CI

Author: Photonios

.circleci/config.yml

@@ -7,7 +7,7 @@ executors:
         type: string
     docker:
       - image: python:<< parameters.version >>-buster
-      - image: postgres:12.0
+      - image: postgres:13.0
         environment:
           POSTGRES_DB: 'psqlextra'
           POSTGRES_USER: 'psqlextra'