wire: Remove deprecated reject message support.

This removes code for accepting reject messages which are no longer
supported by the network.

Since removing the type definition itself would be a major module
version bump, it is not removed at this time and instead the ability to
recognize the message is removed so that any attempts to read the
message will result in a protocol error.

The type and associated test code can be removed on a major module
version bump.

wire/message.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013-2016 The btcsuite developers
-// Copyright (c) 2015-2023 The Decred developers
+// Copyright (c) 2015-2024 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -156,9 +156,6 @@ func makeEmptyMessage(command string) (Message, error) {
 	case CmdGetMiningState:
 		msg = &MsgGetMiningState{}
 
-	case CmdReject:
-		msg = &MsgReject{}
-
 	case CmdSendHeaders:
 		msg = &MsgSendHeaders{}
 

wire/message_test.go

@@ -77,7 +77,6 @@ func TestMessage(t *testing.T) {
 		[]byte("payload"))
 	msgCFHeaders := NewMsgCFHeaders()
 	msgCFTypes := NewMsgCFTypes([]FilterType{GCSFilterExtended})
-	msgReject := NewMsgReject("block", RejectDuplicate, "duplicate block")
 	msgGetInitState := NewMsgGetInitState()
 	msgInitState := NewMsgInitState()
 	msgMixPR, err := NewMsgMixPairReq([33]byte{}, 1, 1, "", 1, 1, 1, 1, []MixPairReqUTXO{}, NewTxOut(0, []byte{}), 1, 1)
@@ -113,7 +112,6 @@ func TestMessage(t *testing.T) {
 		{msgGetHeaders, msgGetHeaders, pver, MainNet, 61},
 		{msgHeaders, msgHeaders, pver, MainNet, 25},
 		{msgMemPool, msgMemPool, pver, MainNet, 24},
-		{msgReject, msgReject, RemoveRejectVersion - 1, MainNet, 79},
 		{msgGetCFilter, msgGetCFilter, pver, MainNet, 57},
 		{msgGetCFHeaders, msgGetCFHeaders, pver, MainNet, 58},
 		{msgGetCFTypes, msgGetCFTypes, pver, MainNet, 24},