Remove tripleo projects from legacy-dsvm-base

These tripleo projects were removed from zuul entirely so it is no
longer valid to have them listed as required projects in zuul jobs. This
cleanup also points out that we can probably clean up the entire
legacy-dsvm-* job structure at this point.

Change-Id: I0e3e43cc0525871b39cc1b85c955bcedddfbe0cf

zuul.d/jobs.yaml

@@ -1141,7 +1141,6 @@
       - openstack/os-brick
       - openstack/os-client-config
       - openstack/os-collect-config
-      - openstack/os-net-config
       - openstack/os-refresh-config
       - openstack/osc-lib
       # NOTE(mriedem): The openstack/placement repo is new in Stein and will
@@ -1150,8 +1149,6 @@
       - openstack/requirements
       - openstack/swift
       - openstack/tempest
-      - openstack/tripleo-heat-templates
-      - openstack/tripleo-image-elements
       - openstack/zaqar
 
 - job: