fix minor issue
<!-- Index Column -->
<ng-container matColumnDef="rowindex">
- <mat-header-cell *matHeaderCellDef mat-sort-header> Index </mat-header-cell>
+ <mat-header-cell *matHeaderCellDef> Index </mat-header-cell>
<mat-cell *matCellDef="let element; let rIndex = index"> {{rIndex}} </mat-cell>
</ng-container>
