Remove China from FBA list

Too many problems right now:

* When you try to ship via FBA, it requires a district, which we haven’t
  even been collecting and which doesn’t apply to all addresses.

* When you try to ship by hand on Amazon.com, it says you need an
  18-digit citizen ID number to get past customs. (!) I don’t know how
  this is handled in FBA. If it is also required, we’d have to figure
  out how to collect it. If it’s not, then I don’t know how they get
  past the customs requirement (and I’m afraid of problems there).

Simplest to just ship these by hand, by volunteers. We don’t get a ton
of requests from China anyway.