Remove empty postcreate file

migration/postcreate.py

-# -*- coding: utf-8 -*-
-# copyright 2013-2014 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
-# contact http://www.logilab.fr -- mailto:contact@logilab.fr
-#
-# This program is free software: you can redistribute it and/or modify it under
-# the terms of the GNU Lesser General Public License as published by the Free
-# Software Foundation, either version 2.1 of the License, or (at your option)
-# any later version.
-#
-# This program is distributed in the hope that it will be useful, but WITHOUT
-# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
-# details.
-#
-# You should have received a copy of the GNU Lesser General Public License along
-# with this program. If not, see <http://www.gnu.org/licenses/>.
-
-"""cubicweb-rqlcontroller postcreate script, executed at instance creation time or when
-the cube is added to an existing instance.
-
-You could setup site properties or a workflow here for example.
-"""
-
-# Example of site property change
-#set_property('ui.site-title', "<sitename>")
-