doc: remove text saying that DFF output inverters are not supported
doc: remove text saying that DFF output inverters are not supported

azonenberg/openfpga,rqou/openfpga,azonenberg/openfpga,rqou/openfpga,rqou/openfpga,rqou/openfpga,azonenberg/openfpga,rqou/openfpga,azonenberg/openfpga,azonenberg/openfpga