🔑 fix wrong variable name in gh action

Author: jaka-k

.github/workflows/hetzner-deploy.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           host: ${{ secrets.HETZNER_HOST }}
           username: root
-          key: ${{ secrets.SSH_PRIVATE_KEY }}
+          key: ${{ secrets.ACTIONS_SSH_KEY }}
           port: 22
           script: |
             cd /home/app/multiagent-rag-system/