message: doc: Fix validation typo
diff: @@ -194,7 +194,7 @@ bool CheckFinalTx(const CBlockIndex* active_chain_tip, const CTransaction &tx, i
  // CheckFinalTx() uses active_chain_tip.Height()+1 to evaluate
  // nLockTime because when IsFinalTx() is called within
  - // CBlock::AcceptBlock(), the height of the block *being*
  + // AcceptBlock(), the height of the block *being*
  // evaluated is what is used. Thus if we want to know if a
  // transaction can be part of the *next* block, we need to call
  // IsFinalTx() with one more than active_chain_tip.Height().
  