Enable swift in tempest-slow-py3 job

Swift is ready on py3 since stable/ussuri and we enabled
it in tempest-full-py3 job for stable/ussuri onwards.

This commit does the same for tempest-slow-py3 job also so that
we can run swift slow test in this job.

Change-Id: I7fa41d4272f792d6fd00bece202c44e342dfeb0a
diff --git a/zuul.d/integrated-gate.yaml b/zuul.d/integrated-gate.yaml
index 8bf53a9..622bbad 100644
--- a/zuul.d/integrated-gate.yaml
+++ b/zuul.d/integrated-gate.yaml
@@ -276,20 +276,9 @@
 - job:
     name: tempest-slow-py3
     parent: tempest-slow
-    vars:
-      devstack_localrc:
-        USE_PYTHON3: true
-      devstack_services:
-        s-account: false
-        s-container: false
-        s-object: false
-        s-proxy: false
-        # without Swift, c-bak cannot run (in the Gate at least)
-        c-bak: false
-    group-vars:
-      subnode:
-        devstack_localrc:
-          USE_PYTHON3: true
+    # This job version is with swift enabled on py3
+    # as swift is ready on py3 from stable/ussuri onwards.
+    branches: ^(?!stable/(ocata|pike|queens|rocky|stein|train)).*$
 
 - job:
     name: tempest-cinder-v2-api