On flavors menu, the _update.html file was deleted.

The openstack_dashboard/dashboards/admin/flavors/templates/
flavors/_update.html is not longer used, so it was deleted.

Change-Id: I88c5b6c75d577cadc1e533a466ecc6489eefcdc8
Closes-Bug: #1288968
Merge "On flavors menu, the _update.html file was deleted."