[webmessaging-tests] Remove a case related to __defineGetter__ (#1436)

The test case should be obsolete, __defineGetter__() is
Non-standard(ref:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__)

View on GitHub: https://github.com/w3c/web-platform-tests/pull/1436

Received on Monday, 1 December 2014 08:19:38 UTC