chore(*): Ensure records are not sorted multi[le times.

Author: MKirova

projects/igniteui-angular/src/lib/grids/pivot-grid/pivot-grid.pipes.ts

@@ -81,6 +81,7 @@ export class IgxPivotRowExpansionPipe implements PipeTransform {
         data.forEach(rec => {
             const keys = Object.keys(rec);
             delete rec.processed;
+            delete rec.sorted;
             //remove all record keys from final data since we don't need them anymore.
             keys.forEach(k => {
                 if (k.indexOf(pivotKeys.records) !== -1) {

projects/igniteui-angular/src/lib/grids/pivot-grid/pivot-util.ts

@@ -47,7 +47,6 @@ export class PivotUtil {
                     rec[k] = this.sort(unsorted, expressions, sorting, pivotKeys);
                 }
             });
-            delete rec.sorted;
         });
         return DataUtil.sort(data, expressions, sorting);
     }