Revise OSOM's service in docker-compose.yaml for file storage

To migrate flowable from in-memory DB to file DB, updates must be made to SPRING_APPLICATION_JSON

Also, does not seem to need a volume attached also so property

    volumes:
    - ./repo:/root

can be removed. Changing file DB data path from ~ to /tmp as well, so it wouldn't mess with the volume if it is needed in the future.