Fix cache invalidate signature method on ApiCache.

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | n/a

Look at HttpKernel\HttpCache::invalidate signature:

https://github.com/symfony/HttpKernel/blob/2.0/HttpCache/HttpCache.php#L243
https://github.com/symfony/HttpKernel/blob/2.1/HttpCache/HttpCache.php#L256
https://github.com/symfony/HttpKernel/blob/2.2/HttpCache/HttpCache.php#L259
https://github.com/symfony/HttpKernel/blob/master/HttpCache/HttpCache.php#L259