Remove skip level upgrade job

SLURP is supported between only .1 releases so upgrade from 2023.1 (or
2023.2) to 2024.2 is not supported.

Change-Id: I8a6b41347b5f07b30320351b5b4ad78e3758e5f8

.zuul.yaml

@@ -187,12 +187,6 @@
       - ^heat/tests/.*$
       - ^releasenotes/.*$
 
-- job:
-    name: grenade-heat-multinode-skip-level
-    parent: grenade-heat-multinode
-    vars:
-      grenade_from_branch: stable/2023.1
-
 - job:
     name: heat-tox-py310-with-sqlalchemy-2x
     parent: openstack-tox-py310
@@ -221,7 +215,6 @@
     check:
       jobs:
         - grenade-heat-multinode
-        - grenade-heat-multinode-skip-level
         - heat-functional
         - heat-functional-legacy
         - heat-functional-centos-9-stream
@@ -229,6 +222,5 @@
     gate:
       jobs:
         - grenade-heat-multinode
-        - grenade-heat-multinode-skip-level
         - heat-functional
         - heat-functional-legacy