Update testIntl.js

Author: FrankYFTang

harness/testIntl.js

@@ -328,7 +328,7 @@ function isCanonicalizedStructurallyValidLanguageTag(locale) {
     // property names must be in lower case; values in canonical form
 
     "art-lojban": "jbo",
-    "cel-gaulish": "xtg-x-cel-gaulish",
+    "cel-gaulish": "xtg",
     "zh-guoyu": "zh",
     "zh-hakka": "hak",
     "zh-xiang": "hsn",