fix: pie label keys are not unique (#4224)

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## Description

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continue to undo key changes... 🙃 

## Related Issue

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#4219

## Motivation and Context

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errors thrown when data is duplicated or when 0 is used as a datapoint

## How Has This Been Tested?

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use 0 as a datapoint and dont log a unique key error

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- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
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- [X] My code follows the code style of this project.
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Co-authored-by: Coltin Kifer <ckifer@amazon.com>

src/polar/Pie.tsx

@@ -467,7 +467,8 @@ export class Pie extends PureComponent<Props, State> {
       }
 
       return (
-        <Layer key={`label-${entry.startAngle}-${entry.endAngle}`}>
+        // eslint-disable-next-line react/no-array-index-key
+        <Layer key={`label-${entry.startAngle}-${entry.endAngle}-${entry.midAngle}-${i}`}>
           {labelLine && Pie.renderLabelLineItem(labelLine, lineProps)}
           {Pie.renderLabelItem(label, labelProps, getValueByDataKey(entry, realDataKey))}
         </Layer>