fixed bug in Apcu driver.

The Apcu driver passes `$stats['mem_size']` to the function `setSize()` of `DriverStatistic`. This generates an error due to type mismatch. The function `setSize()` expects and integer while `$stats['mem_size']` is a float.

Author: afdaniele

lib/Phpfastcache/Drivers/Apcu/Driver.php

@@ -127,6 +127,6 @@ public function getStats(): DriverStatistic
             ->setInfo(\sprintf("The APCU cache is up since %s, and have %d item(s) in cache.\n For more information see RawData.", $date->format(\DATE_RFC2822),
                 $stats['num_entries']))
             ->setRawData($stats)
-            ->setSize($stats['mem_size']);
+            ->setSize((int)$stats['mem_size']);
     }
-}
+}