fix: crrect initialization of a few slices (#12674)

Co-authored-by: Callum Styan <[email protected]>

Author: seiyab

pkg/querier/ingester_querier.go

@@ -269,7 +269,7 @@ func (q *IngesterQuerier) TailersCount(ctx context.Context) ([]uint32, error) {
 		return nil, err
 	}
 
-	counts := make([]uint32, len(responses))
+	counts := make([]uint32, 0, len(responses))
 
 	for _, resp := range responses {
 		counts = append(counts, resp.response.(uint32))

pkg/storage/stores/series/series_index_store.go

@@ -305,7 +305,7 @@ func (c *IndexReaderWriter) chunksToSeries(ctx context.Context, in []logproto.Ch
 		return nil, err
 	}
 
-	results := make([]labels.Labels, len(chunksBySeries)) // Flatten out the per-job results.
+	results := make([]labels.Labels, 0, len(chunksBySeries)) // Flatten out the per-job results.
 	for _, innerSlice := range perJobResults {
 		results = append(results, innerSlice...)
 	}