Add “Overiew” to main Kibana navigation

This was removed here:

#114018

…but Product has requested that it be put back so it is visibe.

src/core/public/chrome/ui/header/collapsible_nav.tsx

@@ -85,7 +85,7 @@ interface Props {
   button: EuiCollapsibleNavProps['button'];
 }
 
-const overviewIDsToHide = ['kibanaOverview', 'enterpriseSearch'];
+const overviewIDsToHide = ['kibanaOverview'];
 const overviewIDs = [
   ...overviewIDsToHide,
   'observability-overview',