Fix Tx json instances #3637

Job	Run time
Build haddock using nix	1m 25s
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	3m 1s
Build specification using nix	1m 7s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	2m 4s
Build & test (plutus-cbor)	1m 18s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/3-nodes.cbor datasets/1-node.cbor --outpu...	5m 15s
Build & test (plutus-merkle-tree)	1m 19s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	1m 34s
Build & test (hydra-plutus)	1m 20s
Build & test (hydra-tui)	2m 28s
Build & test (hydra-node)	4m 15s
Build & test (hydra-cluster)	7m 54s
Publish benchmark results	5s
Publish test results	19s
Documentation	1m 17s
	34m 41s

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