Bump cachix/install-nix-action from V28 to 29 #5630

Job	Run time
Build & test (plutus-cbor)	1m 17s
Build & test (plutus-merkle-tree)	1m 14s
Build & test (hydra-plutus)	1m 18s
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	2m 38s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	1m 40s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/1-node.json datasets/3-nodes.json --outpu...	5m 7s
Build & test (hydra-tui)	2m 55s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	1m 24s
Build haddock using nix	1m 9s
Build & test (hydra-node)	5m 14s
nix flake check	4m 47s
Build & test (hydra-tx)	1m 50s
Build specification using nix	1m 36s
Build & test (hydra-cluster)	7m 54s
Publish benchmark results	4s
Publish test results	13s
Documentation	2m 43s
	43m 3s

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