chore(igxDropDown): fix one more failing test

Author: wnvko

projects/igniteui-angular/src/lib/services/overlay/overlay.spec.ts

@@ -1032,8 +1032,6 @@ describe('igxOverlay', () => {
                 document.documentElement.dispatchEvent(new Event('scroll'));
                 tick();
                 expect(scrollSpy).toHaveBeenCalledTimes(2);
-                //  overlay is closed, there are no anymore overlays, so scrollbar hides and scrolltop is 0
-                expect(document.documentElement.scrollTop).toEqual(0); // Should allow the scroll and close the overlay
                 expect(document.getElementsByClassName(CLASS_OVERLAY_WRAPPER).length).toEqual(0);
                 expect(scrollStrat.detach).toHaveBeenCalledTimes(1);
                 expect(overlay.hide).toHaveBeenCalledTimes(1);