examples/network/fetch.c: revert overzealous conversion of free to git__free

Since git__free is not exported (it's actually a macro), it should not be
used in client programs.  Change this call to 'git__free' back to 'free'.

examples/network/fetch.c

@@ -119,7 +119,7 @@ int fetch(git_repository *repo, int argc, char **argv)
   if (error < GIT_SUCCESS)
     return error;
 
-  git__free(packname);
+  free(packname);
   git_indexer_free(idx);
   git_remote_free(remote);