Make compatible with PHP 8.4

> Http\Client\Common\Plugin\LoggerPlugin::__construct(): Implicitly marking parameter $formatter as nullable is deprecated, the explicit nullable type must be used instead

Author: ruudk

src/LoggerPlugin.php

@@ -23,7 +23,7 @@ final class LoggerPlugin implements Plugin
 
     private $formatter;
 
-    public function __construct(LoggerInterface $logger, Formatter $formatter = null)
+    public function __construct(LoggerInterface $logger, ?Formatter $formatter = null)
     {
         $this->logger = $logger;
         $this->formatter = $formatter ?: new SimpleFormatter();