Use tempest-pg-full

The legacy job legacy-tempest-dsvm-neutron-pg-full is now named
tempest-pg-full - using the new tempest and Zuul v3 frameworks.

Change experimental job to use new job.

Change-Id: If16397724fb4facd2a0db8148bdf7ba427ca10b6
Depends-On: https://review.openstack.org/609530
diff --git a/.zuul.yaml b/.zuul.yaml
index c21fc9e..8520f21 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -597,7 +597,7 @@
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
-        - legacy-tempest-dsvm-neutron-pg-full:
+        - tempest-pg-full:
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$