Rename the "ZF-MG" slice to "MG", and the "ZF-GU" slice to "ZF". Clearer, and reflects common use in the forum and Helios poll.
Rename the "ZF-MG" slice to "MG", and the "ZF-GU" slice to "ZF".
Clearer, and reflects common use in the forum and Helios poll.

Based on https://github.com/zcash/zips/pull/319/commits/1f851eb1c3ef75d34a042e91b6fa878d6969a63a

Co-authored-by: Eran Tromer <a09b99f04bac94993f20a01f321dd533fa9e2be7@tromer.org>
Signed-off-by: Daira Hopwood <cd7d43d5556a38ce626d53826fddc46adc597539@jacaranda.org>

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