[ML] Fix flaky tests for cases attachments (elastic#209143)

## Summary

Increases the timeout for the Cases model assertion to prevent flaky
behavior. The flaky tests runner passed 200/200 ✅—hopefully, it is
stable now.

Closes elastic#203675
Closes elastic#202342
Closes elastic#200836
Closes elastic#196307
Closes elastic#194168

### Checklist

- [x] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed

x-pack/test/functional/services/cases/create.ts

@@ -130,7 +130,7 @@ export function CasesCreateViewServiceProvider(
     async createCaseFromModal(params: CreateCaseParams) {
       await casesCommon.assertCaseModalVisible(true);
 
-      await retry.tryForTime(5000, async () => {
+      await retry.tryForTime(10000, async () => {
         await testSubjects.click('cases-table-add-case-filter-bar');
         await casesCommon.assertCaseModalVisible(false);
       });