ZIP-244: Clarify sapling shared anchor hashing (#490)
ZIP-244: Clarify sapling shared anchor hashing (#490)

* ZIP-244: Clarify sapling shared anchor hashing

Unlike the orchard shared anchor, the sapling v5 transaction shared anchor
is hashed into *each* spend.

* Uppercase Sapling and Spend

Co-authored-by: Deirdre Connolly <8a07e8980a10208dcc9c639c8aae99717076bff0@gmail.com>
zcash/zips,zcash/zips,zcash/zips,zcash/zips