[Synthetics] Fixes action menu (#177408)

closes #177413

## Summary

### Before
<img width="1728" alt="image"
src="https://github.com/elastic/kibana/assets/3505601/bdeaac40-894b-499a-a4e9-651ccb2051b7">


### After

<img width="1727" alt="image"
src="https://github.com/elastic/kibana/assets/3505601/94df1b77-f8c7-4659-8095-cfffdde5749c">

---------

Co-authored-by: Coen Warmer <coen.warmer@gmail.com>

x-pack/plugins/synthetics/public/apps/synthetics/components/common/header/action_menu.tsx

@@ -27,10 +27,12 @@ export const ActionMenu = ({ appMountParameters }: { appMountParameters: AppMoun
         <EuiFlexItem>
           <ActionMenuContent />
         </EuiFlexItem>
+        {ObservabilityAIAssistantActionMenuItem && (
+          <EuiFlexItem>
+            <ObservabilityAIAssistantActionMenuItem />
+          </EuiFlexItem>
+        )}
       </EuiFlexGroup>
-      <EuiFlexItem>
-        {ObservabilityAIAssistantActionMenuItem ? <ObservabilityAIAssistantActionMenuItem /> : null}
-      </EuiFlexItem>
     </HeaderMenuPortal>
   );
 };