Fix comment typo in SignatureHeaderBytes field #3989

Job	Run time
Basic Checks	3m 28s
Unit Tests	10m 2s
Integration Tests (raft)	12m 53s
Integration Tests (pvtdata)	12m 56s
Integration Tests (pvtdatapurge e2e)	21m 55s
Integration Tests (ledger)	15m 27s
Integration Tests (lifecycle)	8m 0s
Integration Tests (smartbft)	21m 14s
Integration Tests (discovery gossip devmode pluggable)	10m 28s
Integration Tests (gateway idemix pkcs11 configtx configtxlator)	18m 53s
Integration Tests (sbe nwo msp)	10m 27s
	2h 25m 43s

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