Use the postgres service instead of pgpool

It seems the bootstrapper does not cater for a replicated postgres url.

client-registry-jempi/docker-compose.combined.yml

@@ -111,7 +111,7 @@ services:
   jempi-bootstrapper:
     image: jembi/jempi-bootstrapper:${JEMPI_BOOTSTRAPPER_IMAGE_TAG}
     environment:
-      POSTGRESQL_IP: ${JEMPI_POSTGRES_DB}
+      POSTGRESQL_IP: ${POSTGRES_SERVICE}
       POSTGRESQL_PORT: 5432
       POSTGRESQL_USER: ${JEMPI_POSTGRESQL_USERNAME}
       POSTGRESQL_PASSWORD: ${JEMPI_POSTGRESQL_PASSWORD}