Replace __sleep/wakeup() by __(un)serialize() for throwing and internal usages

Author: nicolas-grekas

Transport/Smtp/SmtpTransport.php

@@ -372,15 +372,12 @@ private function checkRestartThreshold(): void
         $this->restartCounter = 0;
     }
 
-    public function __sleep(): array
+    public function __serialize(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }
 
-    /**
-     * @return void
-     */
-    public function __wakeup()
+    public function __unserialize(array $data): void
     {
         throw new \BadMethodCallException('Cannot unserialize '.__CLASS__);
     }