Drop Bionic support

Since victoria cycle, we have moved upstream testing to
Ubuntu Focal (20.04) and so does no Bionic distro in
Xena cycle testing runtime[1]. Grenade jobs also started
running on Focal since victoria was released.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2021-May/022248.html

Depends-On: https://review.opendev.org/c/openstack/octavia-tempest-plugin/+/788954

Change-Id: I42e82cdf9dd2fccc3e69689d14a686667431a9a9

zuul.d/jobs.yaml

@@ -8,16 +8,6 @@
         - openstack/octavia
         - openstack/octavia-lib
 
-- job:
-    name: publish-openstack-octavia-amphora-image-bionic
-    parent: publish-openstack-octavia-amphora-image
-    nodeset: ubuntu-bionic
-    description: |
-      Publish Ubuntu Bionic (18.04) based amphora image to tarballs.o.o.
-    vars:
-        amphora_os: ubuntu
-        amphora_os_release: bionic
-
 - job:
     name: publish-openstack-octavia-amphora-image-focal
     parent: publish-openstack-octavia-amphora-image
@@ -41,7 +31,7 @@
 - job:
     name: octavia-grenade
     parent: grenade
-    nodeset: octavia-single-node-ubuntu-bionic
+    nodeset: octavia-single-node-ubuntu-focal
     required-projects:
       - opendev.org/openstack/grenade
       - opendev.org/openstack/octavia
@@ -162,13 +152,13 @@
         - openstack/octavia-lib
     vars:
         amphora_os: ubuntu
-        amphora_os_release: bionic
+        amphora_os_release: focal
 
 - job:
-    name: octavia-amphora-image-build-live-bionic
+    name: octavia-amphora-image-build-live-focal
     parent: octavia-amphora-image-build
     description: |
-      Builds an Ubuntu Bionic amphora image using diskimage-builder from Git
+      Builds an Ubuntu Focal amphora image using diskimage-builder from Git
       master. This job does not publish the image.
     required-projects:
         - openstack/diskimage-builder

zuul.d/projects.yaml

@@ -97,8 +97,6 @@
         - octavia-grenade
     periodic:
       jobs:
-        - publish-openstack-octavia-amphora-image-bionic:
-            branches: ^(?!stable/.*).*$
         - publish-openstack-octavia-amphora-image-focal:
             branches: ^(?!stable/.*).*$
         - publish-openstack-octavia-amphora-image-centos8: