core/types: document JSON field name equivalents of DynamicFeeTx (#24143)

core/types/dynamic_fee_tx.go

@@ -25,8 +25,8 @@ import (
 type DynamicFeeTx struct {
 	ChainID    *big.Int
 	Nonce      uint64
-	GasTipCap  *big.Int
+	GasTipCap  *big.Int // a.k.a. maxPriorityFeePerGas
-	GasFeeCap  *big.Int
+	GasFeeCap  *big.Int // a.k.a. maxFeePerGas
 	Gas        uint64
 	To         *common.Address `rlp:"nil"` // nil means contract creation
 	Value      *big.Int