Fixes Failing test: X-Pack Alerting API Integration Tests.x-pack/test…

…/alerting_api_integration/security_and_spaces/group1/tests/alerting/backfill/task_runner·ts - alerting api integration security and spaces enabled Alerts - Group 1 alerts backfill rule runs ad hoc backfill task should run all execution sets of a scheduled backfill and correctly generate alerts (elastic#191761)

Resolves elastic#183350

## Summary

* Updated rule param that was causing a partial failure in the rule
execution due to maxSignals being greater than the configured allowed
max alerts
* Updated tests to clean the alerts index after every test.

After making these changes, was able to run the flaky test runner 4x200
times without failure.

---------

Co-authored-by: Elastic Machine <[email protected]>

x-pack/test/alerting_api_integration/security_and_spaces/group1/tests/alerting/backfill/task_runner.ts

@@ -86,22 +86,19 @@ export default function createBackfillTaskRunnerTests({ getService }: FtrProvide
     moment().utc().startOf('day').subtract(9, 'days').add(667, 'seconds').toISOString(),
   ];
 
-  // FLAKY: https://github.com/elastic/kibana/issues/183350
-  describe.skip('ad hoc backfill task', () => {
+  describe('ad hoc backfill task', () => {
     beforeEach(async () => {
       await esTestIndexTool.destroy();
       await esTestIndexTool.setup();
     });
     afterEach(async () => {
-      await objectRemover.removeAll();
-      await esTestIndexTool.destroy();
-    });
-    after(async () => {
       await es.deleteByQuery({
         index: alertsAsDataIndex,
         query: { match_all: {} },
         conflicts: 'proceed',
       });
+      await objectRemover.removeAll();
+      await esTestIndexTool.destroy();
     });
 
     // This test
@@ -143,7 +140,7 @@ export default function createBackfillTaskRunnerTests({ getService }: FtrProvide
               from: '1m',
               kibana_siem_app_url: 'https://localhost:5601/app/security',
             },
-            maxSignals: 100,
+            maxSignals: 20,
             riskScore: 21,
             riskScoreMapping: [],
             severity: 'low',