click back in settings region instead of marketplace icon

To fix this failure: http://qa-selenium.mv.mozilla.com:8080/view/Marketplace/job/marketplace.dev.mobile.saucelabs/lastCompletedBuild/testReport/tests.mobile.test_users_account/TestAccounts/test_user_can_go_back_from_settings_page/

Although the test still fails after that because the back button is not supposed to work like `history.back()` in my opinion. The test was passing until yesterday so I assume something has gone wrong.