update comment

Signed-off-by: Ben Ye <[email protected]>

tsdb/db.go

@@ -193,7 +193,7 @@ type Options struct {
 	// BlockQuerierFunc is a function to return storage.Querier from a BlockReader.
 	BlockQuerierFunc BlockQuerierFunc
 
-	// BlockQuerierFunc is a function to return storage.ChunkQuerier from a BlockReader.
+	// BlockChunkQuerierFunc is a function to return storage.ChunkQuerier from a BlockReader.
 	BlockChunkQuerierFunc BlockChunkQuerierFunc
 }