[Security Solution ] Fix flake in `/prebuilt_rules/fleet_integration.…

…ts` API Integration test (#169791)

Fixes: #167056

## Summary

- Flake cannot be reproduced on 500 runs on flaky test runner.
- Latest fail points to [a `socket timeout` error](https://buildkite.com/elastic/kibana-on-merge/builds/36893#018b3d21-52ea-40a5-92a2-24cd2375b525) and not an issue intrinsic to the test; and a subsequent retry makes the test pass.
- **Unskipping test.**


## Flaky test runs

- https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/3728
- https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/3729 [CONTROL - NO CHANGES]

x-pack/test/detection_engine_api_integration/security_and_spaces/prebuilt_rules/fleet_integration.ts

@@ -22,8 +22,7 @@ export default ({ getService }: FtrProviderContext): void => {
   const supertest = getService('supertest');
   const log = getService('log');
 
-  // FLAKY: https://github.com/elastic/kibana/issues/167056
-  describe.skip('install_prebuilt_rules_from_real_package', () => {
+  describe('install_prebuilt_rules_from_real_package', () => {
     beforeEach(async () => {
       await deletePrebuiltRulesFleetPackage(supertest);
       await deleteAllRules(supertest, log);