Drop the classic-frequency table

It comes from ibus-table-chinese, which took it from scim-tables, which
might have taken it from xcin.

All in all, it's not very clear what the licensing is for that file, but
it is very likely that it is GPL.

This might (or might not have the consequence that all of libcangjie
becomes LGPL, and going to court so we get a confirmation is not a very
enjoyable prospect.

This commit drops the file, to clear any possible licensing issue.

In the future, we might get the original contributors to accept to
relicense for us. When that happens, reverting this commit will be
enough to bring back the functionality.