stackdriver: get value type and metric kind from metric descriptor instead of from latest metric result

pkg/tsdb/stackdriver/stackdriver.go

@@ -316,9 +316,6 @@ func (e *StackdriverExecutor) parseResponse(queryRes *tsdb.QueryResult, data Sta
 			Name:   metricName,
 			Points: points,
 		})
-
-		queryRes.Meta.Set("metricKind", series.MetricKind)
-		queryRes.Meta.Set("valueType", series.ValueType)
 	}
 
 	queryRes.Meta.Set("resourceLabels", resourceLabels)