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/misc/fileUtils.js

@@ -90,7 +90,7 @@ function loadInterfaceXML(iface) {
         else
             xml = bytes.toString();
     } catch (e) {
-        log('Failed to load D-Bus interface ' + iface);
+        log(`Failed to load D-Bus interface ${iface}`);
     }
 
     return xml;