skip flaky suite (elastic#189739)

x-pack/plugins/cases/public/components/category/category_form_field.test.tsx

@@ -16,7 +16,8 @@ import { categories } from '../../containers/mock';
 import { MAX_CATEGORY_LENGTH } from '../../../common/constants';
 import { FormTestComponent } from '../../common/test_utils';
 
-describe('Category', () => {
+// FLAKY: https://github.com/elastic/kibana/issues/189739
+describe.skip('Category', () => {
   let appMockRender: AppMockRenderer;
   const onSubmit = jest.fn();