Remove json transaction unmarshaling support for celo transactions legacy transactions retrieved from a celo node.

[piersy]

We should do this some time after we have migrated all celo chains to be L2s.

In celo_transaction_marshaling.go the function celoTransactionUnmarshal has the following code, we simply need to replace if dec.EthCompatible == nil || *dec.EthCompatible == true { with if dec.EthCompatible == nil {

func celoTransactionUnmarshal(dec txJSON, inner *TxData) (bool, error) {
	switch dec.Type {
	case LegacyTxType:
		// EthCompatible is only set to false for celo legacy transactions in the op-geth codebase, otherwise its not
		// set. So not set means it is ethCompatible. However in order to support correct unmarshaling of a celo legacy
		// transaction, retrieved from a celo node (for the purposes of running our api compatibility test) we also need to
		// handle the case where EthCompatible is set to true. 
		if dec.EthCompatible == nil || *dec.EthCompatible == true {
			return false, nil
		}