fix(tests): making the check working

Author: ChronosSF

projects/igniteui-angular/src/lib/date-picker/date-picker.component.spec.ts

@@ -246,7 +246,7 @@ describe('IgxDatePicker', () => {
                 fixture.detectChanges();
 
                 expect(inputGroup.isRequired).toBeFalsy();
-                expect(inputEl.getAttribute('aria-required')).toEqual('false');
+                expect(inputEl.getAttribute('aria-required')).toEqual(null);
             });
 
             it('should set validity to initial when the form is reset', fakeAsync(() => {