Fixed phpdoc typo (#695)

* Fixed phpdoc typo

* Update Builder.php

Author: GrahamCampbell

lib/Github/HttpClient/Builder.php

@@ -5,7 +5,6 @@
 use Http\Client\Common\HttpMethodsClient;
 use Http\Client\Common\Plugin;
 use Http\Client\Common\Plugin\Cache\Generator\HeaderCacheKeyGenerator;
-use Http\Client\Common\PluginClient;
 use Http\Client\Common\PluginClientFactory;
 use Http\Client\HttpClient;
 use Http\Discovery\HttpClientDiscovery;
@@ -34,7 +33,7 @@ class Builder
     /**
      * A HTTP client with all our plugins.
      *
-     * @var PluginClient
+     * @var HttpMethodsClient
      */
     private $pluginClient;