Refactored heatmap chart responsiveness

app/assets/javascripts/monitoring/components/charts/heatmap.vue

 <script>
-import { GlResizeObserverDirective } from '@gitlab/ui';
 import { GlHeatmap } from '@gitlab/ui/dist/charts';
 import { formatDate, timezones, formats } from '../../format_date';
 import { graphDataValidatorForValues } from '../../utils';
@@ -8,9 +7,6 @@ export default {
   components: {
     GlHeatmap,
   },
-  directives: {
-    GlResizeObserverDirective,
-  },
   props: {
     graphData: {
       type: Object,
@@ -61,20 +57,13 @@ export default {
       return this.graphData.metrics[0];
     },
   },
-  methods: {
-    onResize() {
-      if (this.$refs.heatmapChart) return;
-      const { width } = this.$refs.heatmapChart.$el.getBoundingClientRect();
-      this.width = width;
-    },
-  },
 };
 </script>
 <template>
-  <div v-gl-resize-observer-directive="onResize">
   <gl-heatmap
     ref="heatmapChart"
     v-bind="$attrs"
+    :responsive="true"
     :data-series="chartData"
     :x-axis-name="xAxisName"
     :y-axis-name="yAxisName"
@@ -82,5 +71,4 @@ export default {
     :y-axis-labels="yAxisLabels"
     :width="width"
   />
-  </div>
 </template>