Change the fields of REPORT_DOUBLE_VOTE

Author: Seulgi Kim

spec/Dynamic-Validator.md

@@ -205,10 +205,8 @@ The revoke occurs immediately, but the validator cannot be ousted before its ter
 The transaction fails when the delegator revokes more than it delegates.
 
 ### REPORT_DOUBLE_VOTE
-* header1
-* sig1
-* header2
-* sig2
+* message1
+* message2
 
 This is a transaction that reports malicious validator.
 
@@ -223,6 +221,9 @@ The criminal becomes a banned account.
 The account cannot become a candidate anymore.
 In other words, the *DELEGATE* transaction to the banned account and the *SELF_NOMINATE* transaction from the banned account fail.
 
+The type of the messages depends on the consensus engine. For example, type Message type of Tendermint is
+[ConsensusMessage](https://github.com/CodeChain-io/codechain/blob/91125ae49891c375d63e75fd5ac81b0a0d3a9cff/core/src/consensus/tendermint/message.rs#L269).
+
 ## Implementation
 ### States
 ```