Remove unused methods from downloaders

src/Composer/Downloader/GitDownloader.php

@@ -34,11 +34,4 @@ class GitDownloader implements DownloaderInterface
             system('git archive --format=tar --prefix='.escapeshellarg($package->getName()).' --remote='.escapeshellarg($url).' master | tar -xf -');
         }
     }
-
-    public function isDownloaded(PackageInterface $package, $path)
-    {
-        $targetPath = $path . '/' . $package->getName();
-
-        return is_dir($targetPath);
-    }
 }

src/Composer/Downloader/PearDownloader.php

@@ -66,11 +66,4 @@ class PearDownloader implements DownloaderInterface
         }
         chdir($cwd);
     }
-
-    public function isDownloaded(PackageInterface $package, $path)
-    {
-        $targetPath = $path . '/' . $package->getName();
-
-        return is_dir($targetPath);
-    }
 }

src/Composer/Downloader/ZipDownloader.php

@@ -73,11 +73,4 @@ class ZipDownloader implements DownloaderInterface
             throw new \UnexpectedValueException($zipName.' is not a valid zip archive, got error code '.$retval);
         }
     }
-
-    public function isDownloaded(PackageInterface $package, $path)
-    {
-        $targetPath = $path . '/' . $package->getName();
-
-        return is_dir($targetPath);
-    }
 }