set sync2cache frequency from 200s to 400ms, to pass the unit cases

core/txpool/legacypool/legacypool.go

@@ -391,7 +391,7 @@ func (pool *LegacyPool) Init(gasTip uint64, head *types.Header, reserve txpool.A
 }
 
 func (pool *LegacyPool) loopOfSync() {
-	ticker := time.NewTicker(200 * time.Second)
+	ticker := time.NewTicker(400 * time.Millisecond)
 	for {
 		select {
 		case <-pool.reorgShutdownCh: