docs: correct terminology in blockchain.rst #3778

Job	Run time
Basic Checks	1m 21s
Unit Tests	8m 50s
Integration Tests (raft)	12m 4s
Integration Tests (pvtdata)	11m 46s
Integration Tests (pvtdatapurge e2e)	11m 40s
Integration Tests (ledger)	14m 42s
Integration Tests (lifecycle)	6m 51s
Integration Tests (smartbft)	21m 15s
Integration Tests (discovery gossip devmode pluggable)	6m 37s
Integration Tests (gateway idemix pkcs11 configtx configtxlator)	17m 9s
Integration Tests (sbe nwo msp)	8m 24s
	2h 0m 39s

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