Add a note to \crossref{merklepath} clarifying the encoding of rt^Sapling as a primary input to the Sapling spend circuit, and that non-canonical encodings are allowed as input to MerkleCRH^Sapling.
Add a note to \crossref{merklepath} clarifying the encoding of rt^Sapling as a primary input to
the Sapling spend circuit, and that non-canonical encodings are allowed as input to MerkleCRH^Sapling.

Signed-off-by: Daira Hopwood <cd7d43d5556a38ce626d53826fddc46adc597539@jacaranda.org>

zcash/zips,zcash/zips,zcash/zips,zcash/zips