DOC: Remove instruction to demo users to call kill_server()
DOC: Remove instruction to demo users to call kill_server()

which is now unnecessary after making kill_server() happen
automatically when the shell is exited in the demo Director or
Image Repository.

uptane/uptane,shikhar394/uptane,uptane/uptane,awwad/uptane,shikhar394/uptane,awwad/uptane