Replace let with const where variable is never reassigned in Vue files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/views/Discover/Performance/FreqChart.vue

@@ -169,8 +169,8 @@ export default {
       let datasets;
       let datasetsPrimary; // For Compare page case
       let datasetsSecondary; // For Compare page case
-      let minX = chartData?.x_axis?.min;
-      let maxX = chartData?.x_axis?.max;
+      const minX = chartData?.x_axis?.min;
+      const maxX = chartData?.x_axis?.max;
       let xData;
       let primeVueSetData = {};
       let primeVueSetOption = {};