docker-compose: Switch `mongodb` to `mongo` image, remove mongodbbackup
docker-compose: Switch `mongodb` to `mongo` image, remove mongodbbackup

kgjamieson/NEXT,kgjamieson/NEXT,nextml/NEXT,nextml/NEXT,kgjamieson/NEXT,nextml/NEXT,kgjamieson/NEXT,nextml/NEXT