Replace openSUSE tempest check with newer version

We're migrating now to openSUSE 15.0 (yes, 15.0 is newer than 42.3),
remove legacy job legacy-tempest-dsvm-neutron-full-opensuse-423
and replace with native Zuul v3 job tempest-full-py3-opensuse150
running python3.

Remove extra job from experimental queue of devstack-gate, it's
enough to have the job in check pipeline.

Change-Id: Ia6f3407f1387d2f9ea97de6e0665919279511b3c
Depends-On: https://review.openstack.org/609359

zuul.d/projects.yaml

@@ -223,7 +223,7 @@
             voting: false
         - tempest-multinode-full:
             voting: false
-        - legacy-tempest-dsvm-neutron-full-opensuse-423:
+        - tempest-full-py3-opensuse150:
             voting: false
     gate:
       queue: integrated
@@ -236,8 +236,6 @@
         - legacy-tempest-dsvm-neutron-dvr-multinode-full
         - neutron-tempest-dvr-ha-multinode-full
         - legacy-tempest-dsvm-neutron-pg-full
-        - legacy-tempest-dsvm-neutron-full-opensuse-423
-
 
 - project:
     name: openstack-infra/elastic-recheck