Drop opensuse platform job

It has been broken for over a month. Feel free to revert in combination
with a fix, better with a commitment to keep the job in working shape
permanently.

Change-Id: I2604374c23716d56de29e16a459b7c7f45b84891

Author: jharbott

.zuul.yaml

@@ -584,13 +584,6 @@
     voting: false
     timeout: 9000
 
-- job:
-    name: devstack-platform-opensuse-15
-    parent: tempest-full-py3
-    description: openSUSE 15.x platform test
-    nodeset: devstack-single-node-opensuse-15
-    voting: false
-
 - job:
     name: devstack-platform-bionic
     parent: tempest-full-py3
@@ -686,7 +679,6 @@
       jobs:
         - devstack
         - devstack-ipv6
-        - devstack-platform-opensuse-15
         - devstack-platform-fedora-latest
         - devstack-platform-centos-8
         - devstack-platform-bionic