Update doc comment

This should have gone into a previous commit, but I forgot to save
this particular file.

storage/local/interface.go

@@ -53,8 +53,7 @@ type Storage interface {
 	// The iterator will never return samples older than retention time,
 	// relative to the time NewIterator was called.
 	NewIterator(model.Fingerprint) SeriesIterator
-	// Drop all time series associated with the given fingerprints. This operation
-	// will not show up in the series operations metrics.
+	// Drop all time series associated with the given fingerprints.
 	DropMetricsForFingerprints(...model.Fingerprint)
 	// Run the various maintenance loops in goroutines. Returns when the
 	// storage is ready to use. Keeps everything running in the background