[FIX] mass_mailing_egg: use dropzone predicates

Author: thjo-odoo

addons/mass_mailing_egg/static/src/builder/plugins/dropzone_plugin.js

@@ -1,4 +1,5 @@
 import { Plugin } from "@html_editor/plugin";
+import { isPhrasingContent } from "@html_editor/utils/dom_info";
 import { registry } from "@web/core/registry";
 
 class DropzonePlugin extends Plugin {
@@ -47,6 +48,7 @@ class DropzonePlugin extends Plugin {
                 dropNear: ".row:not(.s_col_no_resize) > div",
             },
         ],
+        filter_for_sibling_dropzone_predicates: (el) => isPhrasingContent(el),
     };
 
     get noOptionsSelector() {