Remove the 'jhbuild' folder

This was a nice try, but I never managed to actually make it work.
Remove the mention of libcangjie from the dep list

We don't directly require libcangjie, we require pycangjie (which itself
requires libcangjie).
Remove done TODO

I just went over the 3 projects (libcangjie, pycangjie and
ibus-cangjie) and I think we're now checking for everything properly.