Remove xenial jobs for testing

We no longer have any projects using these jobs, we can delete them.

Change-Id: I2c2aaff0e22434eb176ac1c871712f44902c8461
Depends-On: https://review.openstack.org/623375
Depends-On: https://review.openstack.org/623377
Depends-On: https://review.openstack.org/623368
Depends-On: https://review.openstack.org/623379
Depends-On: https://review.openstack.org/623380
Depends-On: https://review.openstack.org/623381
Depends-On: https://review.openstack.org/623382
Depends-On: https://review.openstack.org/623383
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

.zuul.d/jobs.yaml

@@ -45,11 +45,6 @@
     parent: windmill
     nodeset: ubuntu-bionic
 
-- job:
-    name: windmill-ubuntu-xenial
-    parent: windmill
-    nodeset: ubuntu-xenial
-
 # Testing for install_method: git
 - job:
     name: windmill-src
@@ -78,8 +73,3 @@
     name: windmill-src-ubuntu-bionic
     parent: windmill-src
     nodeset: ubuntu-bionic
-
-- job:
-    name: windmill-src-ubuntu-xenial
-    parent: windmill-src
-    nodeset: ubuntu-xenial

.zuul.d/project-templates.yaml

@@ -21,15 +21,3 @@
       jobs:
         - windmill-ubuntu-bionic
         - windmill-src-ubuntu-bionic
-
-- project-template:
-    name: windmill-jobs-xenial
-    check:
-      jobs:
-        - windmill-ubuntu-xenial
-        - windmill-src-ubuntu-xenial
-    gate:
-      queue: windmill
-      jobs:
-        - windmill-ubuntu-xenial
-        - windmill-src-ubuntu-xenial