Update doc/manuals/user/forbidden_characters.md
Update doc/manuals/user/forbidden_characters.md

Co-authored-by: Alvaro Vega <353fe9019b88407265af4aa01f957f7a9cf6a615@telefonica.com>
telefonicaid/fiware-orion,telefonicaid/fiware-orion,telefonicaid/fiware-orion,telefonicaid/fiware-orion,telefonicaid/fiware-orion,telefonicaid/fiware-orion