Update doc/manuals/admin/database_model.md
Update doc/manuals/admin/database_model.md

Co-authored-by: Ken Zangelin <0c0eb8ee8a8e42b7a52633f50ed380757f36c8fe@gmail.com>
telefonicaid/fiware-orion,telefonicaid/fiware-orion,Fiware/data.Orion,Fiware/data.Orion,telefonicaid/fiware-orion,Fiware/data.Orion,Fiware/data.Orion,telefonicaid/fiware-orion,Fiware/data.Orion,Fiware/data.Orion,telefonicaid/fiware-orion,telefonicaid/fiware-orion