js: Remove dead code in loginDialog and workspacesView

- this._scrolling no longer exists
- _getBannerAllocation takes a single argument

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2042>

js/ui/workspacesView.js

@@ -484,9 +484,6 @@ class WorkspacesView extends WorkspacesViewBase {
     }
 
     _activeWorkspaceChanged(_wm, _from, _to, _direction) {
-        if (this._scrolling)
-            return;
-
         this._scrollToActive();
     }