Bug 1361722 Remove bogus document.write() from test_formdataparsing.js. r=jdm

dom/tests/mochitest/fetch/test_formdataparsing.js

@@ -30,8 +30,6 @@ function testFormDataParsing(fn) {
         boundary + '-',
 
         function(fd) {
-          document.write("0xDEADBEEF");
-          document.write(fd.get("greeting"));
           is(fd.get("greeting"), '"hello"');
         }
       ],