update proto again

Author: yeya24

pkg/querier/tripperware/query.pb.go

@@ -47,7 +47,7 @@ message Extent  {
 message SampleStream {
   repeated cortexpb.LabelPair labels = 1 [(gogoproto.nullable) = false, (gogoproto.jsontag) = "metric", (gogoproto.customtype) = "github.com/cortexproject/cortex/pkg/cortexpb.LabelAdapter"];
   repeated cortexpb.Sample samples = 2 [(gogoproto.nullable) = false, (gogoproto.jsontag) = "values"];
-  repeated SampleHistogramPair histograms = 3 [(gogoproto.nullable) = true, (gogoproto.jsontag) = "histograms"];
+  repeated SampleHistogramPair histograms = 3 [(gogoproto.nullable) = false, (gogoproto.jsontag) = "histograms"];
 }
 
 message SampleHistogramPair {