chore(*): remove the unnecessary tabIndex

Author: ddincheva

projects/igniteui-angular/src/lib/grids/headers/grid-header-group.component.html

@@ -40,7 +40,6 @@
         [attr.aria-label]="column.header || column.field"
         [attr.aria-expanded]="column.expanded"
         [attr.aria-selected]="column.selected"
-        tabindex="0"
         [ngClass]="{
             'igx-grid__th--pinned-last': hasLastPinnedChildColumn,
             'igx-grid__th--pinned-first': hasFirstPinnedChildColumn,
@@ -51,6 +50,7 @@
         [ghostHost]="grid.outletDirective.nativeElement"
         [attr.droppable]="true"
         [igxColumnMovingDrop]="column"
+        (pointerdown)="activate()"
         (click)="groupClicked($event)"
         (pointerenter)="onPinterEnter()"
         (pointerleave)="onPointerLeave()"
@@ -80,7 +80,7 @@
 
 <ng-container *ngIf="!column.columnGroup">
     <span *ngIf="grid.hasMovableColumns" class="igx-grid__th-drop-indicator-left"></span>
-    <igx-grid-header [igxColumnMovingDrag]="column" [ghostHost]="grid.outletDirective.nativeElement" [attr.droppable]="true" [igxColumnMovingDrop]="column" [gridID]="column.grid.id" [column]="column"></igx-grid-header>
+    <igx-grid-header [igxColumnMovingDrag]="column" [ghostHost]="grid.outletDirective.nativeElement" [attr.droppable]="true" (pointerdown)="activate()" [igxColumnMovingDrop]="column" [gridID]="column.grid.id" [column]="column"></igx-grid-header>
     <igx-grid-filtering-cell *ngIf="grid.allowFiltering && grid.filterMode == 'quickFilter'" [column]="column" [attr.draggable]="false"></igx-grid-filtering-cell>
     <span *ngIf="!column.columnGroup && column.resizable" class="igx-grid__th-resize-handle"
           [igxResizeHandle]="column"