Fixed EZP-21037: content staging error synchronizing a subtree (part 2)

The duplicated part of the code removed in
kernel/content/copysubtree.php were not removed in
bin/php/ezsubtreecopy.php
Merge pull request #706 from patrickallaert/EZP-21037

Fixed EZP-21037: content staging error synchronizing a subtree (part 2)