[REM] theme_*: remove snippet options after website refactor

*: theme_clean, theme_common, theme_enark

Following the website refactor [1], that code is not used anymore.

[1]: https://github.com/odoo/odoo/commit/9fe45e2b7ddbbfd0445ffe25a859e67a316d02b2

closes odoo/design-themes#1125

Related: odoo/odoo#218357
Related: odoo/enterprise#89955
Related: odoo/upgrade#8131
Signed-off-by: Serge Bayet (seba) <seba@odoo.com>

theme_common/static/src/js/compatibility_editor.js

@@ -1,17 +0,0 @@
-/** @odoo-module **/
-
-import sOptions from "@web_editor/js/editor/snippets.options";
-
-sOptions.registry.BackgroundImage.include({
-    /**
-     * @override
-     */
-    background: function (previewMode, widgetValue, params) {
-        this._super.apply(this, arguments);
-
-        var customClass = this.$target.attr('class').match(/\b(bg-img-\d+)\b/);
-        if (customClass) {
-            this.$target.removeClass(customClass[1]);
-        }
-    },
-});