Temporary workaround for stuck zoom on older Firefox versions

`scrollend` event is just not called if rapidly scrolling with mouse wheel and pressing Cmd/Ctrl to zoom.
The problem doesn’t occur on Firefox 132, and possibly some earlier versions

web/app.js

@@ -2115,7 +2115,7 @@ const PDFViewerApplication = {
       }
 
       mainContainer.removeEventListener("scroll", scroll);
-      this._isScrolling = true;
+      // this._isScrolling = true;
       mainContainer.addEventListener("scrollend", scrollend, { signal });
       mainContainer.addEventListener("blur", scrollend, { signal });
     };