whisper: fix megacheck warnings (#14925)

* whisper: fix megacheck warnings

* whisper/whisperv5: regenerate json codec to fix unused override type

whisper/whisperv2/api.go

@@ -377,15 +377,6 @@ func (w *whisperFilter) retrieve() (messages []WhisperMessage) {
 	return
 }
 
-// activity returns the last time instance when client requests were executed on
-// the filter.
-func (w *whisperFilter) activity() time.Time {
-	w.lock.RLock()
-	defer w.lock.RUnlock()
-
-	return w.update
-}
-
 // newWhisperFilter creates a new serialized, poll based whisper topic filter.
 func newWhisperFilter(id hexutil.Uint, ref *Whisper) *whisperFilter {
 	return &whisperFilter{

whisper/whisperv2/whisper.go

@@ -173,7 +173,7 @@ func (self *Whisper) Send(envelope *Envelope) error {
 // Start implements node.Service, starting the background data propagation thread
 // of the Whisper protocol.
 func (self *Whisper) Start(*p2p.Server) error {
-	log.Info(fmt.Sprint("Whisper started"))
+	log.Info("Whisper started")
 	go self.update()
 	return nil
 }
@@ -182,7 +182,7 @@ func (self *Whisper) Start(*p2p.Server) error {
 // of the Whisper protocol.
 func (self *Whisper) Stop() error {
 	close(self.quit)
-	log.Info(fmt.Sprint("Whisper stopped"))
+	log.Info("Whisper stopped")
 	return nil
 }