Disable final part of tests/feature/Object.js pending wider adoption …

…of node 4.1; see issue #1991

@arv TBR

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1992

Closes #1992.

Author: johnjbarton

test/feature/Symbol/Object.js

@@ -21,9 +21,11 @@ assert.isTrue(n in object);
 assert.isTrue(delete object[n]);
 assert.isFalse(n in object);
 
+/* TODO(jjb): Issue #1991
 var keys = [];
 for (var k in object) {
-  keys.push(k);
+	keys.push(k);
 }
 assert.equal(0, keys.length, keys + '');
 assert.equal(0, Object.keys(object).length);
+*/