[FIX] website: fix missed forward-port

A forward-port ported this commit:
https://github.com/odoo/odoo/commit/c12f2cd5ccc72a680ab741b4ce16d3913dd3854e#diff-473476fda8a8b38a9ee4480eb2bf2e2eR150
But ignored that a more recent one did remove the related code:
https://github.com/odoo/odoo/commit/0eafeab1#diff-473476fda8a8b38a9ee4480eb2bf2e2eL173

The result was misindented breaking code.

addons/website/static/src/js/website.snippets.editor.js

@@ -218,9 +218,6 @@ options.registry.carousel = options.registry.slider.extend({
 
         // set background and prepare to clean for save
         this.$target.on('slid.bs.carousel', function () {
-                self.editor.styles.background_position.$target = self.editor.styles.background.$target;
-                self.editor.styles.background_position.set_active();
-                self.editor.styles.background.$target.trigger("snippet-option-change", [self.editor.styles.background]);
             self.$target.carousel("pause");
             if (!self.editor) return;