Stop gating on ubuntu-xenial

There is no issues running ubuntu-bionic, so stop gating on
ubuntu-xenial to save us CI resources.

Change-Id: I1caedaee17b67d27a7005a827be62a58c9739a49
Depends-On: https://review.openstack.org/623074
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

.zuul.yaml

@@ -24,11 +24,6 @@
     parent: ansible-role-nodepool
     nodeset: ubuntu-bionic
 
-- job:
-    name: ansible-role-nodepool-ubuntu-xenial
-    parent: ansible-role-nodepool
-    nodeset: ubuntu-xenial
-
 # Testing for nodepool_install_method: git
 - job:
     name: ansible-role-nodepool-src
@@ -49,34 +44,23 @@
     parent: ansible-role-nodepool-src
     nodeset: ubuntu-bionic
 
-- job:
-    name: ansible-role-nodepool-src-ubuntu-xenial
-    parent: ansible-role-nodepool-src
-    nodeset: ubuntu-xenial
-
 - project:
-    name: openstack/ansible-role-nodepool
     templates:
       - windmill-jobs-fedora-latest
       - windmill-jobs-bionic
-      - windmill-jobs-xenial
     check:
       jobs:
         - ansible-role-nodepool-fedora-latest
         - ansible-role-nodepool-ubuntu-bionic
-        - ansible-role-nodepool-ubuntu-xenial
         - ansible-role-nodepool-src-fedora-latest
         - ansible-role-nodepool-src-ubuntu-bionic
-        - ansible-role-nodepool-src-ubuntu-xenial
         - tox-linters
         - windmill-tox-molecule
     gate:
       jobs:
         - ansible-role-nodepool-fedora-latest
         - ansible-role-nodepool-ubuntu-bionic
-        - ansible-role-nodepool-ubuntu-xenial
         - ansible-role-nodepool-src-fedora-latest
         - ansible-role-nodepool-src-ubuntu-bionic
-        - ansible-role-nodepool-src-ubuntu-xenial
         - tox-linters
         - windmill-tox-molecule