docs: correct terminology in blockchain.rst #3779

Job	Run time
Basic Checks	1m 13s
Unit Tests	8m 17s
Integration Tests (raft)	12m 5s
Integration Tests (pvtdata)	11m 46s
Integration Tests (pvtdatapurge e2e)	10m 57s
Integration Tests (ledger)	13m 34s
Integration Tests (lifecycle)	6m 11s
Integration Tests (smartbft)	19m 37s
Integration Tests (discovery gossip devmode pluggable)	5m 59s
Integration Tests (gateway idemix pkcs11 configtx configtxlator)	16m 34s
Integration Tests (sbe nwo msp)	8m 13s
	1h 54m 26s

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