Drop bindep-opensuse-15 job

The OpenDev team is planning to remove OpenSUSE LEAP 15 images as our
node builds and mirrors are for 15.2 which is ancient and no one is
currently working to modernize these test environments. On top of that
LEAP is apparently going away in the future and will be replaced with
another distro.

Bindep's unittesting of platforms with mocked out /etc/os-release based
distro detection should be sufficient testing for suse going forward.

Change-Id: I9f8f79bc6957932725f6da28934d4494c3335d15

.zuul.yaml

@@ -20,11 +20,6 @@
     parent: bindep-base
     nodeset: centos-8-stream
 
-- job:
-    name: bindep-opensuse-15
-    parent: bindep-base
-    nodeset: opensuse-15
-
 - job:
     name: bindep-ubuntu-xenial
     parent: bindep-base
@@ -49,7 +44,6 @@
       jobs:
         - bindep-centos-7
         - bindep-centos-8-stream
-        - bindep-opensuse-15
         - bindep-ubuntu-xenial
         - bindep-ubuntu-bionic
         - bindep-ubuntu-focal
@@ -66,7 +60,6 @@
       jobs:
         - bindep-centos-7
         - bindep-centos-8-stream
-        - bindep-opensuse-15
         - bindep-ubuntu-xenial
         - bindep-ubuntu-bionic
         - bindep-ubuntu-focal