fix(policy): remove DELETE method from Discord preset

Discord bots rarely need DELETE access. Removing it reduces the
attack surface for sandbox agents interacting with Discord APIs.

Fixes #1433

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: miyoungc

nemoclaw-blueprint/policies/presets/discord.yaml

@@ -19,7 +19,6 @@ network_policies:
           - allow: { method: POST, path: "/**" }
           - allow: { method: PUT, path: "/**" }
           - allow: { method: PATCH, path: "/**" }
-          - allow: { method: DELETE, path: "/**" }
       # WebSocket gateway — must use access: full (CONNECT tunnel) instead
       # of protocol: rest. The proxy's HTTP idle timeout (~2 min) kills
       # long-lived WebSocket connections; a CONNECT tunnel avoids