Test Slack integration for multinode workflow

Author: markgoddard

.github/workflows/stackhpc-multinode.yml

@@ -52,7 +52,7 @@ name: Multinode
 jobs:
   multinode:
     name: Multinode
-    uses: stackhpc/stackhpc-openstack-gh-workflows/.github/workflows/multinode.yml@1.0.0
+    uses: stackhpc/stackhpc-openstack-gh-workflows/.github/workflows/multinode.yml@slack
     with:
       multinode_name: ${{ inputs.multinode_name }}
       os_distribution: ${{ inputs.os_distribution }}
@@ -68,4 +68,5 @@ jobs:
       # NOTE(upgrade): Reference the PREVIOUS release here.
       stackhpc_kayobe_config_previous_version: stackhpc/2023.1
       terraform_kayobe_multinode_version: ${{ inputs.terraform_kayobe_multinode_version }}
+      enable_slack_alert: true
     secrets: inherit