Delete vocabulary/* as it's maintained in spec/* (#138)
    
    "... `vocabulary/` folder looks important but it's outdated and everything in it is either already in the spec or in issues. It was created very early, ... . It's not needed anymore and probably would just confuse people who find it ..."
    
    So remove it.
    
    Co-authored-by: 6543 <6543@obermui.de>
    Reviewed-on: https://codeberg.org/ForgeFed/ForgeFed/pulls/138
    Reviewed-by: fr33domlover <fr33domlover@noreply.codeberg.org>
    Reviewed-by: Ta180m <ta180m@noreply.codeberg.org>