[FIX] web_editor: fix double Shift + Enter

Pressing Shift + Enter twice was buggy because of small refactoring
made by https://github.com/odoo/odoo/commit/c227b8fd88e0ed635a8e807501b559b46fee7786#diff-cc5180b5ec2395c1df5c4e475aff43fbL416

opw-806003

addons/web_editor/static/src/js/rte.summernote.js

@@ -422,6 +422,9 @@ dom.isImg = function (node) {
 };
 var fn_is_forbidden_node = dom.isForbiddenNode || function () {};
 dom.isForbiddenNode = function (node) {
+    if (node.tagName === "BR") {
+        return false;
+    }
     return fn_is_forbidden_node(node) || $(node).is(".media_iframe_video");
 };
 var fn_is_img_font = dom.isImgFont || function () {};