chore(deps): update docker.io/library/postgres docker tag to v16.6

docker-compose/authentik/compose.yaml

@@ -1,7 +1,7 @@
 ---
 services:
   postgres:
-    image: docker.io/library/postgres:16.5
+    image: docker.io/library/postgres:16.6
     container_name: authentik-db
     environment:
       - POSTGRES_USER=${POSTGRES_USER:-authentik}