CONN-27 Fixed pulling avatar in Special:Connect

* removed `class_exists( 'Masthead' );` call since Masthead is [enabled sitewide](https://github.com/Wikia/app/blob/dev/extensions/wikia/UserProfilePageV3/UserProfilePage.setup.php#L28),
* left upload to `UserProfilePageController` since it's also [enabled sitewide](https://github.com/Wikia/config/blob/dev/CommonExtensions.php#L1714)