Revert "Fix "undefiend" typo in unreserved-words.js (#1816)" (#1819)

This reverts commit 7e659997.

test/language/reserved-words/unreserved-words.js

@@ -99,7 +99,7 @@ var typeid = 1;
 // u
 var uint = 1;
 var unchecked = 1;
-var undefined = 1;
+var undefiend = 1;
 var union = 1;
 var unsafe = 1;
 var unsigned = 1;