Bug 1470873 - Part 2 - Resume running formautofill xpcshell tests in non-headless mode. r=bgrins

Differential Revision: https://phabricator.services.mozilla.com/D12027

--HG--
extra : rebase_source : ceeae763ef3020343084dd94134a1fc365ad90d3

browser/extensions/formautofill/test/unit/xpcshell.ini

@@ -1,6 +1,5 @@
 [DEFAULT]
 firefox-appdir = browser
-headless = true
 head = head.js
 support-files =
   ../fixtures/**