peer: Remove unused version sent field.

This removes the field that tracks whether the version has been sent
since it is no longer used after the version negotiation was separated
from the main read and write code.

peer/peer.go

@@ -405,7 +405,6 @@ type Peer struct {
 	advertisedProtoVer   uint32 // protocol version advertised by remote
 	protocolVersion      uint32 // negotiated protocol version
 	sendHeadersPreferred bool   // peer sent a sendheaders message
-	versionSent          bool
 	verAckReceived       bool
 
 	knownInventory     *mruInventoryMap
@@ -2017,14 +2016,7 @@ func (p *Peer) writeLocalVersionMsg() error {
 		return err
 	}
 
-	if err := p.writeMessage(localVerMsg); err != nil {
-		return err
-	}
-
-	p.flagsMtx.Lock()
-	p.versionSent = true
-	p.flagsMtx.Unlock()
-	return nil
+	return p.writeMessage(localVerMsg)
 }
 
 // negotiateInboundProtocol waits to receive a version message from the peer