Removed unused Silencer import

src/Composer/Repository/PlatformRepository.php

@@ -16,7 +16,6 @@ use Composer\Package\CompletePackage;
 use Composer\Package\PackageInterface;
 use Composer\Package\Version\VersionParser;
 use Composer\Plugin\PluginInterface;
-use Composer\Util\Silencer;
 
 /**
  * @author Jordi Boggiano <j.boggiano@seld.be>