Fix flaky alert flapping test (#198013)

Resolves #195573

In this PR, I'm un-skipping the alerts as data flapping tests. The flaky
test runners weren't able to reproduce the flakiness. I believe it's
because we needed to wait longer after changing the flapping settings
for the cache to clear. This is already done in
https://github.com/elastic/kibana/pull/197070/files#diff-3d57bae0b495bddd934b87ca29e2f43fa21bab9bf304b5d359d7e230284415c0
but it was merged after the test was skipped.

Flaky test runners:
-
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/7286
-
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/7293
-
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/7306

x-pack/test/alerting_api_integration/spaces_only/tests/alerting/group4/alerts_as_data/alerts_as_data_flapping.ts

@@ -35,8 +35,7 @@ export default function createAlertsAsDataFlappingTest({ getService }: FtrProvid
 
   const alertsAsDataIndex = '.alerts-test.patternfiring.alerts-default';
 
-  // Failing: See https://github.com/elastic/kibana/issues/195573
-  describe.skip('alerts as data flapping', function () {
+  describe('alerts as data flapping', function () {
     this.tags('skipFIPS');
     beforeEach(async () => {
       await es.deleteByQuery({