Fix dropdown-menu reducer test

app/soapbox/reducers/__tests__/dropdown-menu.test.ts

@@ -3,9 +3,7 @@ import reducer from '../dropdown-menu';
 describe('dropdown_menu reducer', () => {
   it('should return the initial state', () => {
     expect(reducer(undefined, {} as any).toJS()).toEqual({
-      openId: null,
-      placement: null,
-      keyboard: false,
+      isOpen: false,
     });
   });
 });