fix docker compose port allocation for local dev (#117)

change docker compose port to right prometheus port

Author: dat2

docker-compose.yml

@@ -14,4 +14,4 @@ services:
       - "${PWD}/examples/docker/pgcat.toml:/etc/pgcat/pgcat.toml"
     ports:
       - "6432:6432"
-      - "9090:9090"
+      - "9930:9930"