js: Remove unused catch bindings

Optional catch bindings have been supported for quite a while now,
so we can treat unused error bindings in catch statements like any
other unused variable.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3684>

js/ui/audioDeviceSelection.js

@@ -190,7 +190,7 @@ export class AudioDeviceSelectionDBus {
         let dialog;
         try {
             dialog = new AudioDeviceSelectionDialog(devices);
-        } catch (e) {
+        } catch {
             invocation.return_value(null);
             return;
         }