Remove zh-[cn|tw] in favour of zh-han[s|t]

Change-Id: I9580a6ee3d32408c0ef74e565a3a0e793eb1f27c
Reviewed-on: https://gerrit.wikimedia.org/r/125150
Reviewed-by: Raimond Spekking <raimond.spekking@gmail.com>
Tested-by: Raimond Spekking <raimond.spekking@gmail.com>