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/ui/unlockDialog.js

@@ -99,7 +99,7 @@ var UnlockDialog = class {
             this._authPrompt.cancel();
     }
 
-    _otherUserClicked(button, event) {
+    _otherUserClicked() {
         Gdm.goto_login_session_sync(null);
 
         this._authPrompt.cancel();