gas: drop scrubber states 14 and 15

While sadly 52628315 doesn't say anything on why these would have
been needed, the latest with the removal of most of the opcode vs
operands distinction in the scrubber these shouldn't be needed anymore.
The implementation was a little questionable anyway, in moving back to
states expecting labels, when clearly labels shouldn't really be
following predicates (in practice, due to another bug, at least ia64
permits such).