fix(docs): Fix NU6-related documentation #1996

Job	Run time
Generate crates matrix	21s
Check crates matrix	5s
Build zebrad crate	36m 58s
Build zebra-utils crate	16m 47s
Build zebra-test crate	1m 38s
Build zebra-state crate	22m 14s
Build zebra-script crate	3m 24s
Build zebra-scan crate	26m 58s
Build zebra-rpc crate	34m 26s
Build zebra-node-services crate	3m 35s
Build zebra-network crate	6m 56s
Build zebra-grpc crate	15m 29s
Build zebra-consensus crate	17m 17s
Build zebra-chain crate	5m 8s
Build tower-fallback crate	1m 7s
Build tower-batch-control crate	1m 30s
Open or update issues for building crates individually failures	0s
	3h 13m 53s

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