Remove the legacy integration tests job

The tests should be fixed in master/stein first, because the integration
test frameworks is available from horizon only for those releases.
As the frameworks is unlikely to be backported, there is no point
in keeping a broken version of a native job.

If the integration tests are fixed at some point, this decision can be
re-evaluated.

This was discussed during the Sahara weekly meeting:
http://eavesdrop.openstack.org/meetings/sahara/2019/sahara.2019-02-28-14.01.log.html#l-109

Change-Id: I311203779bd3e6c6660cfe1b84e89c7dc0825c98
(cherry picked from commit ea3a84ac4e)

.zuul.yaml

@@ -10,9 +10,6 @@
         - sahara-dashboard-tox-py27-dj110:
             voting: false
             branches: ^(?!stable/ocata).*$
-        - legacy-sahara-dashboard-dsvm-integration:
-            voting: false
-
     gate:
       jobs:
         - sahara-dashboard-tox-py27-dj19