[CI] Drop unused nodeset

It is required for infra cleanup.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2021-December/026408.html

Change-Id: I6479e84b57bb988e7196f781644bb8f62b1f0406

Author: yoctozepto

zuul.d/nodesets.yaml

@@ -1,10 +1,4 @@
 ---
-- nodeset:
-    name: kolla-ansible-centos8
-    nodes:
-      - name: primary
-        label: centos-8
-
 - nodeset:
     name: kolla-ansible-centos8s
     nodes:
@@ -51,16 +45,6 @@
       - name: secondary2
         label: ubuntu-focal
 
-- nodeset:
-    name: kolla-ansible-centos8-multi
-    nodes:
-      - name: primary
-        label: centos-8
-      - name: secondary1
-        label: centos-8
-      - name: secondary2
-        label: centos-8
-
 - nodeset:
     name: kolla-ansible-centos8s-multi
     nodes:
@@ -77,34 +61,12 @@
       - name: primary
         label: nested-virt-ubuntu-focal
 
-- nodeset:
-    name: kolla-ansible-centos8-nested-virt
-    nodes:
-      - name: primary
-        label: nested-virt-centos-8
-
 - nodeset:
     name: kolla-ansible-centos8s-nested-virt
     nodes:
       - name: primary
         label: nested-virt-centos-8-stream
 
-- nodeset:
-    name: kolla-ansible-centos8-multi-monasca
-    nodes:
-      - name: primary
-        label: centos-8
-      - name: secondary1
-        label: centos-8
-      - name: secondary2
-        label: centos-8
-      - name: secondary3
-        label: centos-8
-      - name: secondary4
-        label: centos-8
-      - name: secondary5
-        label: centos-8
-
 - nodeset:
     name: kolla-ansible-centos8s-multi-monasca
     nodes: