core: move balanceCheck addition in buyGas (ethereum#29762)

It's a bit confusing to add msg.value into the balanceCheck within the conditional.
No impact on block validation since GasFeeCap is always set when processing transactions.

core/state_transition.go

@@ -240,8 +240,9 @@ func (st *StateTransition) buyGas() error {
 	if st.msg.GasFeeCap != nil {
 		balanceCheck.SetUint64(st.msg.GasLimit)
 		balanceCheck = balanceCheck.Mul(balanceCheck, st.msg.GasFeeCap)
-		balanceCheck.Add(balanceCheck, st.msg.Value)
 	}
+	balanceCheck.Add(balanceCheck, st.msg.Value)
+
 	if st.evm.ChainConfig().IsCancun(st.evm.Context.BlockNumber, st.evm.Context.Time) {
 		if blobGas := st.blobGasUsed(); blobGas > 0 {
 			// Check that the user has enough funds to cover blobGasUsed * tx.BlobGasFeeCap