Fix permissions for promote workflow

Author: Alex-Welsh

.github/workflows/stackhpc-promote.yml

@@ -10,7 +10,8 @@ jobs:
     name: Trigger Pulp promotion workflows
     if: github.repository == 'stackhpc/stackhpc-kayobe-config'
     runs-on: ubuntu-latest
-    permissions: {}
+    permissions:
+      actions: write
     steps:
       # NOTE(mgoddard): Trigger another CI workflow in the
       # stackhpc-release-train repository.