fixup! go/proto/msgpack: Fix Error -> ErrorCode is int on the wire and not extension type

go/neo/proto/proto_test.go

@@ -176,7 +176,7 @@ func TestMsgMarshal(t *testing.T) {
 		// uint32(N)/enum(M), string
 		{&Error{Code: 0x00000045, Message: "hello"},
 			"\x00\x00\x00\x45\x00\x00\x00\x05hello",
-			hex("92") + hex("d40245") + "\xc4\x05hello",
+			hex("92") + hex("45") + "\xc4\x05hello",
 		},
 
 		// Oid, Tid, bool, Checksum, []byte