ZIP 316: correct the rationale for the minimum size of the Bech32m-decoded byte sequence.
ZIP 316: correct the rationale for the minimum size of the Bech32m-decoded byte sequence.

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

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