core: fix formatting error (trailing whitepace)

core/blockchain.go

@@ -62,7 +62,7 @@ var (
 	blockWriteTimer      = metrics.NewRegisteredTimer("chain/write", nil)
 
 	blockPrefetchExecuteTimer   = metrics.NewRegisteredTimer("chain/prefetch/executes", nil)
-	blockPrefetchInterruptMeter = metrics.NewRegisteredMeter("chain/prefetch/interrupts", nil)	
+	blockPrefetchInterruptMeter = metrics.NewRegisteredMeter("chain/prefetch/interrupts", nil)
 )
 
 const (