stackdriver: use correct event name

public/app/plugins/datasource/stackdriver/query_aggregation_ctrl.ts

@@ -23,7 +23,7 @@ export class StackdriverAggregationCtrl {
     this.setAlignOptions();
     $scope.onAlignmentChange = this.onAlignmentChange.bind(this);
     $scope.onAggregationChange = this.onAggregationChange.bind(this);
-    $scope.$on('metricTypeChange', this.setAlignOptions.bind(this));
+    $scope.$on('metricTypeChanged', this.setAlignOptions.bind(this));
   }
 
   onAlignmentChange(newVal: string) {

public/app/plugins/datasource/stackdriver/query_ctrl.ts

@@ -194,7 +194,7 @@ export class StackdriverQueryCtrl extends QueryCtrl {
     const { valueType, metricKind } = this.metricDescriptors.find(m => m.type === this.target.metricType);
     this.target.valueType = valueType;
     this.target.metricKind = metricKind;
-    this.$scope.$broadcast('metricTypeChange');
+    this.$scope.$broadcast('metricTypeChanged');
     this.refresh();
     this.getLabels();
   }