Revert "chart.js: Update ChartData to accept both Arrays and ReadonlyArrays (#42023)"

This reverts commit dc72f7ed97.

types/chart.js/chart.js-tests.ts

@@ -411,15 +411,6 @@ if (doughnutChart.getDatasetMeta(0).data.length > 0) {
     console.log(doughnutChartView.y);
 }
 
-// Passing readonly data as ChartData
-const readonlyDataInput: {
-    labels: ReadonlyArray<string>;
-    datasets: ReadonlyArray<{
-        data: number[];
-    }>;
-} = { labels: [], datasets: [] };
-const readonlyData: Chart.ChartData = readonlyDataInput;
-
 // Time Cartesian Axis
 const timeAxisChartData: Chart.ChartData = {
     datasets: [{

types/chart.js/index.d.ts

@@ -243,8 +243,8 @@ declare namespace Chart {
     }
 
     interface ChartData {
-        labels?: ReadonlyArray<string | ReadonlyArray<string> | number | ReadonlyArray<number> | Date | ReadonlyArray<Date> | Moment | ReadonlyArray<Moment>>;
-        datasets?: ReadonlyArray<ChartDataSets>;
+        labels?: Array<string | string[] | number | number[] | Date | Date[] | Moment | Moment[]>;
+        datasets?: ChartDataSets[];
     }
 
     interface RadialChartOptions extends ChartOptions {