customembed: don't parse in xmlMode

This fixes an issue where <params> weren't being parsed correctly
because they are self-closing HTML5 tags.

lib/customembed.js

@@ -11,8 +11,7 @@ function sha256(input) {
 function filter(input) {
     var $ = cheerio.load(input, {
         lowerCaseTags: true,
-        lowerCaseAttributeNames: true,
-        xmlMode: true
+        lowerCaseAttributeNames: true
     });
     var meta = getMeta($);
     var id = "cu:" + sha256(input);