chore: Update some dated comments (#2031)

* chore: Update some dated comments

* Remove old protocol version comment

Author: palango

consensus/istanbul/backend/handler.go

@@ -36,7 +36,6 @@ var (
 	errDecodeFailed = errors.New("fail to decode istanbul message")
 )
 
-// If you want to add a code, you need to increment the Lengths Array size!
 const (
 	handshakeTimeout = 5 * time.Second
 )

consensus/istanbul/protocol.go

@@ -22,10 +22,6 @@ import (
 
 // Constants to match up protocol versions and messages
 const (
-	// No longer supported, can be removed.
-	// The corresponding version upstream (eth/66) is removed in upstream PR #23120.
-	// Celo66 = 66
-
 	// Supported versions
 	Celo67 = 67 // incorporates changes from eth/66 (EIP-2481)
 )
@@ -38,13 +34,8 @@ const ProtocolName = "istanbul"
 var ProtocolVersions = []uint{Celo67}
 
 // protocolLengths are the number of implemented message corresponding to different protocol versions.
-var ProtocolLengths = map[uint]uint64{Celo67: 25}
-
-// NOTICE:
 // celo/67, uses as the last message the 0x18, so it has 25 messages (including the 0x00)
-// celo/66 has 27 as an unharm effect of removing 2 messages before the mainnet launch, that were
-// never updated with the actual number (https://github.com/celo-org/celo-blockchain/pull/893)
-// The Celo66 protocol has actually 25 messages, but we keep it with 27 to avoid problems.
+var ProtocolLengths = map[uint]uint64{Celo67: 25}
 
 // Message codes for istanbul related messages
 // If you want to add a code, you need to increment the protocolLengths Array size