docker: use mysql and postgres from latest fake-data-gen

docker/blocks/postgres/docker-compose.yaml

@@ -7,3 +7,10 @@
     ports:
       - "5432:5432"
     command: postgres -c log_connections=on -c logging_collector=on -c log_destination=stderr -c log_directory=/var/log/postgresql
+
+  fake-postgres-data:
+    image: grafana/fake-data-gen
+    network_mode: bridge
+    environment:
+      FD_DATASOURCE: postgres
+      FD_PORT: 5432