removes hardcoded "prefer-source" in ArchiveManage when calling

DownloadManager

src/Composer/Package/Archiver/ArchiveManager.php

@@ -138,7 +138,7 @@ class ArchiveManager
             $filesystem->ensureDirectoryExists($sourcePath);
 
             // Download sources
-            $this->downloadManager->download($package, $sourcePath, true);
+            $this->downloadManager->download($package, $sourcePath);
         }
 
         // Create the archive