Small fixups from going through the "Open a head on testnet" tutorial #4217

Job	Run time
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	2m 55s
Build & test (plutus-cbor)	1m 32s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	2m 1s
Build & test (plutus-merkle-tree)	1m 33s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/1-node.json datasets/3-nodes.json --outpu...	5m 4s
Build haddock using nix	1m 15s
Build & test (hydra-plutus)	1m 26s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	1m 43s
Build & test (hydra-tui)	2m 25s
Build & test (hydra-node)	4m 22s
Build specification using nix	1m 2s
Build & test (hydra-cluster)	6m 1s
nix flake check	4m 3s
Publish benchmark results	5s
Publish test results	1s
Documentation	1s
	35m 29s

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