Remove xenial-arm64 wheel jobs

Nothing uses Xenial on ARM64, and we don't want anything to start, so
let's remove the nodes.  This removes the wheel publishing jobs.

Change-Id: Ib268fe7379e3d1a98e1fbe30233c156834d65c36
Depends-On: https://review.opendev.org/c/openstack/project-config/+/789493
Depends-On: https://review.opendev.org/c/openstack/requirements/+/789487
Depends-On: https://review.opendev.org/c/openstack/requirements/+/789488
Depends-On: https://review.opendev.org/c/openstack/requirements/+/789490

zuul.d/jobs.yaml

@@ -1618,20 +1618,3 @@
         wheel_python: python2
       wheel-cache-ubuntu-xenial-python3:
         wheel_python: python3
-
-- job:
-    name: build-wheel-cache-ubuntu-xenial-arm64
-    parent: build-wheel-cache-base
-    description: |
-      Build Ubuntu Xenial ARM64 wheels for OpenStack CI mirrors.
-    nodeset:
-      nodes:
-        - name: wheel-cache-ubuntu-xenial-arm64-python2
-          label: ubuntu-xenial-arm64
-        - name: wheel-cache-ubuntu-xenial-arm64-python3
-          label: ubuntu-xenial-arm64
-    host-vars:
-      wheel-cache-ubuntu-xenial-arm64-python2:
-        wheel_python: python2
-      wheel-cache-ubuntu-xenial-arm64-python3:
-        wheel_python: python3

zuul.d/project.yaml

@@ -45,10 +45,6 @@
             files:
               - playbooks/wheel-cache
               - roles/build-wheel-cache
-        - build-wheel-cache-ubuntu-xenial-arm64:
-            files:
-              - playbooks/wheel-cache
-              - roles/build-wheel-cache
         - build-wheel-cache-ubuntu-bionic-arm64:
             files:
               - playbooks/wheel-cache