Remove support for openSUSE since Python 3.6 is no longer supported

The conditions are left in the code in case someone somehow make it
work. We can clean them up later.

Change-Id: I65f6da0e90560c00eb82e8e4366fdaf3bbde8da1

dib/ironic-python-agent-ramdisk/environment.d/20-ipa-distro-family.bash

@@ -1,4 +1,3 @@
-# TODO(dtantsur): verify if opensuse can be added here
 if [[ $DISTRO_NAME =~ (fedora|centos|rhel) ]]; then
     export IPA_DISTRO_FAMILY=rh
 else

doc/source/admin/dib.rst

@@ -9,7 +9,6 @@ real hardware. The recommended distributions are:
 
 The following should work but receive only limited testing and support:
 
-* openSUSE Leap 15.1
 * Ubuntu 20.04 Focal
 
 Building

releasenotes/notes/no-suse-e15d8384c423251c.yaml

@@ -0,0 +1,4 @@
+---
+upgrade:
+  - |
+    Support for openSUSE Leap 15.* has been removed.

zuul.d/ironic-python-agent-builder-jobs.yaml

@@ -109,15 +109,6 @@
     vars:
       extra_elements: ["extra-hardware"]
 
-- job:
-    name: ironic-python-agent-check-image-dib-opensuse
-    parent: ironic-python-agent-check-image-base
-    required-projects:
-      - openstack/diskimage-builder
-    vars:
-      image_type: 'dib'
-      image_distro: 'opensuse'
-
 - job:
     name: ironic-python-agent-check-image-dib-debian
     parent: ironic-python-agent-check-image-base

zuul.d/project.yaml

@@ -17,8 +17,6 @@
         # Non-voting jobs
         - ironic-python-agent-check-image-dib-ubuntu:
             voting: false
-        - ironic-python-agent-check-image-dib-opensuse:
-            voting: false
         - ipa-tempest-bios-ipmi-direct-src:
             voting: false
         - ipa-tempest-ironic-inspector-src: