[REM] website: remove forgotten compatibility code for sign-in option

Commit [1] was not adapted properly for its master version.

[1]: https://github.com/odoo/odoo/commit/68ed032b8ac29431550846a60189f4f32223d68a

Related to task-3474743

Part-of: odoo/odoo#119650

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

@@ -2259,23 +2259,6 @@ options.registry.HeaderLayout = options.registry.WebsiteLevelColor.extend({
     }
 });
 
-options.registry.HeaderExtraElts = options.Class.extend({
-
-    //--------------------------------------------------------------------------
-    // Public
-    //--------------------------------------------------------------------------
-
-    /**
-     * @override
-     */
-    async start() {
-        await this._super(...arguments);
-        // TODO Remove in master.
-        const signInOptionEl = this.el.querySelector('[data-customize-website-views="portal.user_sign_in"]');
-        signInOptionEl.dataset.noPreview = 'true';
-    },
-});
-
 options.registry.HeaderNavbar = options.Class.extend({
     /**
      * Particular case: we want the option to be associated on the header navbar

addons/website/views/snippets/snippets.xml

@@ -987,8 +987,7 @@
             data-page-option-name="header_text_color"/>
     </div>
 
-    <div data-js="HeaderExtraElts"
-         data-selector="#wrapwrap > header"
+    <div data-selector="#wrapwrap > header"
          data-no-check="true"
          groups="website.group_website_designer">
         <we-row string="Elements" class="o_we_full_row align-items-start">