No need to synchronize fetch

The individual RPC clients are synchronized, and we can safely talk
to more than one client at the same time.

src/main/java/org/deepsymmetry/cratedigger/FileFetcher.java

@@ -292,7 +292,7 @@ private DirOpResBody find (InetAddress player, String mountPath, String filePath
      *
      * @throws IOException if there is a problem retrieving the file
      */
-    public synchronized void fetch(InetAddress player, String mountPath, String sourcePath, File destination) throws IOException {
+    public void fetch(InetAddress player, String mountPath, String sourcePath, File destination) throws IOException {
         FileOutputStream outputStream = new FileOutputStream(destination);
         try {
             // Make sure the file exists on the player, and find its file handle.