Facets in the "blocks" realm settings page should not have drag and drop weights

The realm settings page allows for facets to be weighted via a drag and drop interface so that the order they are displayed on the search page can be configured via the UI. This is useful for ordering facets that are rendered as form elements, as in the "fieldset" realm. The order of facets in the "blocks" realm are configured via the core block UI, so having configurable weights in Facet API doesn't make sense for this realm. This may cause confusion since the weights set in the Facet API interface don't actually do anything useful in the context of the "blocks" realm.