doc: Fix validation typo

Author: MarcoFalke

src/validation.cpp

@@ -191,7 +191,7 @@ 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().