Fix docker-compose.yml version warning [skip ci] (#211)

> "the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"

Author: omad

docker/docker-compose.yml

@@ -1,4 +1,3 @@
-version: "3.7"
 services:
   postgres:
     image: postgis/postgis:10-2.5