[FIX] mass_mailing: add markup to preview mobile dialog

This fix is only a missing of the commit 7f5a0ccf9e5fdf3f7fece8a9.
As a reminder, in 7f5a0ccf9e5fdf3f7fece8a9, we check that the content of
the dialog is markuped. If not, we escape it.
So in this commit, we add the markup to the "props.preview".

closes odoo/odoo#138494

Signed-off-by: Mathieu Duckerts-Antoine (dam) <dam@odoo.com>

addons/mass_mailing/static/src/js/mass_mailing_html_field.js

@@ -13,7 +13,7 @@ import { HtmlField, htmlField } from "@web_editor/js/backend/html_field";
 import { MassMailingMobilePreviewDialog } from "./mass_mailing_mobile_preview";
 import { getRangePosition } from '@web_editor/js/editor/odoo-editor/src/utils/utils';
 import { utils as uiUtils } from "@web/core/ui/ui_service";
-import { useSubEnv, status } from "@odoo/owl";
+import { useSubEnv, status, markup } from "@odoo/owl";
 
 export class MassMailingHtmlField extends HtmlField {
     static props = {
@@ -265,7 +265,7 @@ export class MassMailingHtmlField extends HtmlField {
             });
             this.mobilePreview = this.dialog.add(MassMailingMobilePreviewDialog, {
                 title: _t("Mobile Preview"),
-                preview: mailingHtml.body.innerHTML,
+                preview: markup(mailingHtml.body.innerHTML),
             }, {
                 onClose: () => $previewBtn.prop('disabled', false),
             });