FIX: Show search context only in topic routes (PR #14650)

Fixes an issue where the “in this topic” indicator in the quick search widget would remain visible even after having navigated away from the topic route.


Isn’t this.router.currentRouteName enough or do we have to use the private _router ?

Sure, I based my change off existing code, but currentRouteName sure is cleaner. (Removed the other references to the private _router while at it.)