When you next update your Discourse installation, the widget rendering system will now be disabled, and any widget-based customization won’t be rendered anymore.
For now, on incompatible sites, the admin can re-enable the old behavior by modifying the values of the following setting:
deactivate_widgets_rendering
This is the final phase before removing the old code from the Discourse code base, which is expected to happen in about a month. Subsequently, it won’t be possible to re-enable widgets anymore.