Add opcode_size for nop so we don't get errors #964

Job	Run time
docker-master	1h 31m 40s
test-standalone (master, dev, default)	1m 27s
publish-standalone-dry-run	16s
validate-docker-master	2m 26s
build-js-of-ocaml (master, 4.11.1)	5m 51s
standalone-haskell (master)	51m 20s
build-wasm-of-ocaml (master, 4.14.1)	18m 53s
generated-files (master)	22m 24s
test-amd64	2h 18m 6s
deploy-js-wasm-of-ocaml	1m 30s
docker-check-all	3s
	5h 33m 56s

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