windowManager: Limit super-scroll handling to normal mode

The overview has it's own workspace scroll handling, and we don't want
to switch workspaces in other modes. Limiting the scroll-event handler
to NORMAL mode matches the swipe tracker used by WorkspaceAnimation,
and allows for other uses of scroll events (like scrolling in the
alt-tab popup).

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3840

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1746>

js/ui/windowManager.js

@@ -864,6 +864,10 @@ var WindowManager = class {
                            this._switchToApplication.bind(this));
 
         global.stage.connect('scroll-event', (stage, event) => {
+            const allowedModes = Shell.ActionMode.NORMAL;
+            if ((allowedModes & Main.actionMode) === 0)
+                return Clutter.EVENT_PROPAGATE;
+
             if (this._workspaceAnimation.canHandleScrollEvent(event))
                 return Clutter.EVENT_PROPAGATE;