Remove platform-dependent mozc::Encryptor part 3

This is just a removal of an unused file, which should have been removed in r208.  Hence no behavior change is intended with this CL.

BUG=Issue mozc:215
TEST=compile

git-svn-id: https://mozc.googlecode.com/svn/trunk@497 a6090854-d499-a067-5803-1114d4e51264