cleanup: Prefer template strings

Template strings are much nicer than string concatenation, so use
them where possible; this excludes translatable strings and any
strings containing '/' (until we can depend on gettext >= 0.20[0]).

[0] https://savannah.gnu.org/bugs/?50920

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/612

js/ui/appDisplay.js

@@ -151,7 +151,7 @@ class BaseAppView {
         if (this._items[id])
             this._items[id].actor.navigate_focus(null, St.DirectionType.TAB_FORWARD, false);
         else
-            log('No such application ' + id);
+            log(`No such application ${id}`);
     }
 
     selectApp(id) {