PhpDoc fix in AbstractRememberMeServices

All extending classes return `UserInterface`, not TokenInterface:

* https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/Security/Http/RememberMe/TokenBasedRememberMeServices.php#L64
* https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/Security/Http/RememberMe/PersistentTokenBasedRememberMeServices.php#L116

And `AbstractRememberMeServices` actually required the return value to be `UserInterface`:

            $user = $this->processAutoLoginCookie($cookieParts, $request);

            if (!$user instanceof UserInterface) {
                throw new \RuntimeException('processAutoLoginCookie() must return a UserInterface implementation.');
            }

src/Symfony/Component/Security/Http/RememberMe/AbstractRememberMeServices.php

@@ -217,7 +217,7 @@ abstract class AbstractRememberMeServices implements RememberMeServicesInterface
      * @param array   $cookieParts
      * @param Request $request
      *
-     * @return TokenInterface
+     * @return UserInterface
      */
     abstract protected function processAutoLoginCookie(array $cookieParts, Request $request);