Don't run requirements integration for Grizzly

* modules/openstack_project/files/zuul/layout.yaml: The
.*-requirements-integration-dsvm jobs are dependent on requirements
list normalization and some related mechanisms in the
openstack/requirements project which were developed during the
Havana release cycle and not backported to the stable/grizzly
branch, so we cannot expect them to run reliably their in the
present state.

Change-Id: I55c5179b302f322075c415b40949918b1b630398
Merge "Don't run requirements integration for Grizzly"