NimbusFeatures.urlbar.ready never resolves (QuickSuggest never initialises)

One quirk I noticed when testing new quick suggest stuff is that the QuickSuggest.init method never resolves. This is because it has

await lazy.NimbusFeatures.urlbar.ready();

which never resolves. The main effect is that QuickSuggest is never loaded with any features. This is not a big deal since QuickSuggest is not enabled (browser.urlbar.quicksuggest.enabled is false) so these features shouldn't be called anyway.

But we should investigate why NimbusFeatures is hanging and whether this might cause problems elsewhere or in the future.