`sc-chain-spec`: deprecated code removed #837

Job	Run time
set-image	12s
check-runtime-migration (asset-hub-westend)	3m 53s
check-runtime-migration (asset-hub-rococo)	14m 23s
check-runtime-migration (bridge-hub-westend)	3m 49s
check-runtime-migration (bridge-hub-rococo)	4m 2s
check-runtime-migration (contracts-rococo)	8m 14s
check-runtime-migration (collectives-westend)	3m 53s
check-runtime-migration (coretime-rococo)	3m 53s
	42m 19s

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