[SKIP FLAKY ON MKI] common/../search_source_alert.ts (elastic#194110)

## Summary

see details: elastic#193842

While only skipping
`x-pack/test_serverless/functional/test_suites/common/discover_ml_uptime/discover/search_source_alert.ts`,
hopefully
`x-pack/test/functional_with_es_ssl/apps/discover_ml_uptime/discover/search_source_alert.ts`
will not have to be skipped soon as well.

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/test_serverless/functional/test_suites/common/discover_ml_uptime/discover/search_source_alert.ts

@@ -365,7 +365,9 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
     expect(await titleElem.getAttribute('value')).to.equal(dataView);
   };
 
-  describe('Search source Alert', () => {
+  describe('Search source Alert', function () {
+    // see details: https://github.com/elastic/kibana/issues/193842
+    this.tags(['failsOnMKI']);
     before(async () => {
       await security.testUser.setRoles(['discover_alert']);
       await PageObjects.svlCommonPage.loginAsAdmin();