Fix slack catalog entry

Author: slimslenderslacks

prompts/catalog.yaml

@@ -582,6 +582,7 @@ registry:
     icon: https://cdn.jsdelivr.net/npm/simple-icons@v7/icons/slack.svg
     secrets:
       - name: slack.team_id
+      - name: slack.bot_token
   redis:
     description: interact with Slack Workspaces
     ref: github:docker/labs-ai-tools-for-devs?path=prompts/mcp/slack.md