Small fixups from going through the "Open a head on testnet" tutorial #4209

Job	Run time
Build & test (plutus-cbor)	1m 27s
Build & test (plutus-merkle-tree)	1m 30s
Build haddock using nix	1m 15s
Build & test (hydra-plutus)	1m 34s
Build & test (hydra-tui)	2m 21s
nix flake check	47m 7s
Build & test (hydra-node)	4m 25s
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	2m 43s
Build & test (hydra-cluster)	7m 42s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	2m 7s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/1-node.json datasets/3-nodes.json --outpu...	5m 19s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	1m 40s
Build specification using nix	54s
Publish test results	18s
Publish benchmark results	18s
Documentation	1m 33s
	1h 22m 13s

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