Rename some section titles under 'Consensus Changes from Bitcoin' to use 'Encoding and Consensus'.
Rename some section titles under 'Consensus Changes from Bitcoin' to use 'Encoding and Consensus'.

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

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