Modify codeviewFilter: true so setting is opt out rather than opt in.

This is after a discussion on PR#3782 to set the filter to true, so it becomes an opt out option rather than opt in to filtering options are on by default due to XSS issues referenced to the PR#3782

src/js/base/settings.js

@@ -232,7 +232,7 @@ $.summernote = $.extend($.summernote, {
       lineNumbers: true,
     },
 
-    codeviewFilter: false,
+    codeviewFilter: true,
     codeviewFilterRegex: /<\/*(?:applet|b(?:ase|gsound|link)|embed|frame(?:set)?|ilayer|l(?:ayer|ink)|meta|object|s(?:cript|tyle)|t(?:itle|extarea)|xml)[^>]*?>/gi,
     codeviewIframeFilter: true,
     codeviewIframeWhitelistSrc: [],