cleanup: 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-extensions/-/merge_requests/413>
(cherry picked from commit 3a76b9eec4)

extensions/apps-menu/extension.js

@@ -488,7 +488,7 @@ class ApplicationsButton extends PanelMenu.Button {
                 let id;
                 try {
                     id = entry.get_desktop_file_id(); // catch non-UTF8 filenames
-                } catch (e) {
+                } catch {
                     continue;
                 }
                 let app = appSys.lookup_app(id);