Increase timeout for firefoxos.123done.org due to test failure

I'm not crazy about doing this, but the failure at [1] seems to show that the page hadn't fully loaded when the test failed [2].

[1] http://qa-selenium.mv.mozilla.com:8080/view/B2G%20Inari/job/b2g.inari.gaia.v1.0.1.ui.ril/11/testReport/%28root%29/TestPersonaCookie/test_persona_cookie/?
[2] http://qa-selenium.mv.mozilla.com:8080/view/B2G%20Inari/job/b2g.inari.gaia.v1.0.1.ui.ril/11/testReport/(root)/TestPersonaCookie/attachments/test_persona_cookie_screenshot.png