Drop tripleo centos-7 scen3 job definition - not used

This is needed by [1] where this job is being removed. Note
that this job as defined will only run for stable/stein [2].
Also note that this job doesn't appear to be running anywhere
it is not wired up in this repo [3] or anywhere else.

Cherrypick is not clean, it makes sahara-openstack-ansible-functional
non voting as requested in review comments [4]. This part is
specific to Victoria and Ussuri.

Also sets openstack-tox-lower-constraints as non voting per review
comments here.

[1] https://review.opendev.org/c/openstack/tripleo-ci/+/838110/2#message-2efaca7aaf100874fd6996f18f0e74ae942149c0
[2] 4daed1b14c/zuul.d/standalone-jobs.yaml (L476)
[3] https://codesearch.opendev.org/?q=sahara-tripleo-ci-centos-7-scenario003-standalone&i=nope&literal=nope&files=&excludeFiles=&repos=
[4] https://review.opendev.org/c/openstack/sahara/+/838017/3#message-3cddf211ea5974fb65c92c148dd9ec52594ac1e2

(cherry-picked from commit 4175be12a6)

Change-Id: I7a4071e52f68fea7d07bad690f8590cbb3fb4fa4

.zuul.yaml

@@ -19,6 +19,8 @@
             nodeset: ubuntu-bionic
         - sahara-grenade
         - sahara-openstack-ansible-functional
+        - openstack-tox-lower-constraints:
+            voting: false
     gate:
       queue: sahara
       jobs:
@@ -29,7 +31,8 @@
         - requirements-check:
             nodeset: ubuntu-bionic
         - sahara-grenade
-        - sahara-openstack-ansible-functional
+        - openstack-tox-lower-constraints:
+            voting: false
     experimental:
       jobs:
         - sahara-buildimages-ambari
@@ -97,18 +100,11 @@
       - ^tools/.*$
       - ^tox.ini$
 
-- job:
-    name: sahara-tripleo-ci-centos-7-scenario003-standalone
-    description: |
-      Basic TripleO standalone job with all Sahara API tests
-    parent: tripleo-ci-centos-7-scenario003-standalone
-    vars:
-      featureset_override:
-        tempest_test_whitelist:
-          - 'sahara_tempest_plugin.tests.api.'
-
+# Job set non voting as it in unstable for ussuri
+# https://review.opendev.org/c/openstack/sahara/+/838017/3#message-3cddf211ea5974fb65c92c148dd9ec52594ac1e2
 - job:
     name: sahara-openstack-ansible-functional
+    voting: false
     description: |
       OSA job focused on openstack-ansible-os_sahara
     parent: openstack-ansible-cross-repo-functional