Revert "kolla: Replace Ubuntu 20.04 nodeset with Ubuntu 22.04"

This reverts commit 899106a8d21c02867b44c3717bca5e58486e0756.

Change-Id: I1e3252dc39444ed838e54c4bb61942c326a2a990
diff --git a/zuul.d/sp-cinder.yaml b/zuul.d/sp-cinder.yaml
index 6352343..25e96f1 100644
--- a/zuul.d/sp-cinder.yaml
+++ b/zuul.d/sp-cinder.yaml
@@ -236,7 +236,7 @@
     required-projects:
       - opendev.org/openstack/tempest
     timeout: 10800
-    nodeset: ubuntu2204-openstack-multi-node-mixed
+    nodeset: ubuntu2004-openstack-multi-node-mixed
     attempts: 1
     secrets:
       # openstack-client