Make test pass for the right reason

Previously, the `nextTick` wasn't awaited, which meant that the on-call
schedules list wasn't rendered anyway.

This also makes sure the previous wrapper is destroyed before creating
a new one for this test.

spec/frontend/members/components/modals/leave_modal_spec.js

@@ -99,10 +99,14 @@ describe('LeaveModal', () => {
       });
     });
 
-    it("does NOT display oncall schedules list when member's user is NOT a part of on-call schedules ", () => {
+    it("does NOT display oncall schedules list when member's user is NOT a part of on-call schedules ", async () => {
+      wrapper.destroy();
+
       const memberWithoutOncallSchedules = cloneDeep(member);
       delete memberWithoutOncallSchedules.user.oncallSchedules;
       createComponent({ member: memberWithoutOncallSchedules });
+      await nextTick();
+
       expect(findOncallSchedulesList().exists()).toBe(false);
     });
   });