correctly format donut chart center value on hover (#4686)

* consistent pie chart formatting

* format title on hover

frontend/src/metabase/visualizations/visualizations/PieChart.jsx

@@ -184,8 +184,8 @@ export default class PieChart extends Component<*, Props, *> {
 
         let value, title;
         if (hovered && hovered.index != null && slices[hovered.index] !== otherSlice) {
-            title = slices[hovered.index].key;
-            value = slices[hovered.index].value;
+            title = formatDimension(slices[hovered.index].key);
+            value = formatMetric(slices[hovered.index].value);
         } else {
             title = "Total";
             value = formatMetric(total);