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/environment.js

@@ -111,7 +111,7 @@ function init() {
         let base = origToString.call(this);
         try {
             if ('actor' in this && this.actor instanceof Clutter.Actor)
-                return base.replace(/\]$/, ' delegate for ' + this.actor.toString().substring(1));
+                return base.replace(/\]$/, ` delegate for ${this.actor.toString().substring(1)}`);
             else
                 return base;
         } catch (e) {