Rename the heat-translator project repo

Rename the project repo from stackforge/heat-translator
to openstack/heat-translator.
The heat-translator project has been recently added to
the Heat program,
https://review.openstack.org/#/c/127349/

Co-Authored-By: Sergey Lukjanov <slukjanov@mirantis.com>

Change-Id: I1fc734ba437ad089ba465aba8f49e68faa372ade
Merge "Rename the heat-translator project repo"