[AO] Fix flaky test (elastic#166179)

## Summary

It fixes elastic#165619
## Notes:
- The issue wasn't related to the `/_alertSummary` endpoint and wouldn't
be fixed after merging the new update from ResponsOps PR. (tested here
with a clone PR elastic#166273)
- The failing test is so little flaky only **0.5%** , after each update
I run the flaky-test-runner to run 400 times.
- The issue seems related to three things that has been done:
   - Waiting for the rule details page to load
   - Use LogThreshold instead of the Uptime rule
- The mocking lib seems to miss the mock sometimes with Uptime and makes
the real function be called without a `featureIds`

## DoD
- The PR has been tested 2 x 400 = 800 times with 0 fails ->
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/3100

x-pack/test/observability_functional/apps/observability/pages/rule_details_page.ts

@@ -36,8 +36,7 @@ export default ({ getService }: FtrProviderContext) => {
     return true;
   }
 
-  // FLAKY: https://github.com/elastic/kibana/issues/165619
-  describe.skip('Observability Rule Details page', function () {
+  describe('Observability Rule Details page', function () {
     this.tags('includeFirefox');
 
     let uptimeRuleId: string;
@@ -149,10 +148,14 @@ export default ({ getService }: FtrProviderContext) => {
 
     describe('Alert summary widget component', () => {
       before(async () => {
-        await observability.alerts.common.navigateToRuleDetailsByRuleId(uptimeRuleId);
+        await observability.alerts.common.navigateToRuleDetailsByRuleId(logThresholdRuleId);
+        await retry.waitFor(
+          'Rule details to be visible',
+          async () => await testSubjects.exists('ruleDetails')
+        );
       });
 
-      it('shows component on the rule detils page', async () => {
+      it('shows component on the rule details page', async () => {
         await observability.components.alertSummaryWidget.getCompactComponentSelectorOrFail();
 
         const timeRangeTitle =