Update LineTimeSerieChart tooltip formatting and add unitRange to PercentageChartExample story

Author: ziyang-lin-404

src/lib/components/charts/linetimeseries/LineTimeSerieChart.tsx

@@ -172,7 +172,7 @@ const LineTimeSerieChartTooltip = ({
 
             const formattedValue = !Number.isFinite(entry.value)
               ? '-'
-              : `${entry.value.toFixed(2)} ${unitLabel}`;
+              : `${entry.value.toFixed(2)}${unitLabel ? ` ${unitLabel}` : ''}`;
 
             return (
               <React.Fragment key={index}>

stories/linetimeseriechart.stories.tsx

@@ -502,6 +502,7 @@ export const PercentageChartExample: Story = {
     helpText: 'This is the help text',
     yAxisType: 'percentage',
     yAxisTitle: '',
+    unitRange: [{ threshold: 1, label: '%' }],
     interval: SAMPLE_FREQUENCY_LAST_TWENTY_FOUR_HOURS,
     duration: SAMPLE_DURATION_LAST_TWENTY_FOUR_HOURS,
     xAxisFormat: 'date-time',