Remove py36 lib master testing job

Below patch moving lib master testing to py39
- https://review.opendev.org/c/openstack/openstack-zuul-jobs/+/842646

and depends on replacing the below py36 jobs usage
to py39. Witht that we can remove the below py36 jobs.
- openstack-tox-py36-with-neutron-lib-master
- openstack-tox-py36-with-oslo-master
- openstack-tox-py36-with-ovsdbapp-master

Depends-On: https://review.opendev.org/c/openstack/project-config/+/842843
Change-Id: I87070e249637942330d084115774fe960d03787a

zuul.d/jobs.yaml

@@ -843,60 +843,6 @@
     vars:
       tox_install_siblings: true
 
-- job:
-    name: openstack-tox-py36-with-oslo-master
-    parent: openstack-tox-with-oslo-master-base
-    nodeset: ubuntu-bionic
-    description: |
-      This job installs all oslo libraries from source and tests that the
-      unit tests of the tested project work.
-
-      It uses the tox ``py36`` environment.
-
-      The job is normally run in a periodic pipeline, it is configured
-      to run on the master branch.
-    branches: master
-    vars:
-      tox_envlist: py36
-      bindep_profile: test py36
-
-- job:
-    name: openstack-tox-py36-with-neutron-lib-master
-    parent: openstack-tox-py36
-    timeout: 3000
-    description: |
-      This job installs neutron-lib from source and tests that the
-      unit tests of the tested project work.
-
-      It uses the tox ``py36`` environment.
-
-      The job is normally run in a periodic pipeline, it is configured
-      to run on the master branch.
-    branches: master
-    required-projects:
-      - openstack/neutron
-      - openstack/neutron-lib
-    vars:
-      tox_install_siblings: true
-
-- job:
-    name: openstack-tox-py36-with-ovsdbapp-master
-    parent: openstack-tox-py36
-    timeout: 3000
-    description: |
-      This job installs ovsdbapp from source and tests that the
-      unit tests of the tested project work.
-
-      It uses the tox ``py36`` environment.
-
-      The job is normally run in a periodic pipeline, it is configured
-      to run on the master branch.
-    branches: master
-    required-projects:
-      - openstack/ovsdbapp
-    vars:
-      tox_install_siblings: true
-
 - job:
     name: openstack-tox-py39-with-oslo-master
     parent: openstack-tox-with-oslo-master-base