Mention in validation that IsWitnessStandard tests for P2TR

src/validation.cpp

@@ -696,7 +696,7 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
         return state.Invalid(TxValidationResult::TX_INPUTS_NOT_STANDARD, "bad-txns-nonstandard-inputs");
     }
 
-    // Check for non-standard witness in P2WSH
+    // Check for non-standard witnesses.
     if (tx.HasWitness() && fRequireStandard && !IsWitnessStandard(tx, m_view))
         return state.Invalid(TxValidationResult::TX_WITNESS_MUTATED, "bad-witness-nonstandard");