cleanup: Remove some unhelpful unused arguments

Those unused arguments aren't bugs - unbeknownst to eslint, they all
correspond to valid signal parameters - but they don't contribute
anything to clarity, so just remove them anyway.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/627

js/perf/hwtest.js

@@ -38,7 +38,7 @@ function waitAndDraw(milliseconds) {
     let timeline = new Clutter.Timeline({ duration: milliseconds });
     timeline.start();
 
-    timeline.connect('new-frame', (timeline, frame) => {
+    timeline.connect('new-frame', (_timeline, _frame) => {
         global.stage.queue_redraw();
     });