Fix issue triage agent: remove lockdown mode

Remove lockdown: true from the issue triage agent workflow. Lockdown
requires a GH_AW_GITHUB_TOKEN secret which is not configured. The
default mode with roles-based access control is sufficient for this
public demo repo.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: codebytes

.github/workflows/issue-triage-agent.lock.yml

@@ -8,8 +8,6 @@ permissions:
   issues: read
 tools:
   github:
-    # For now we are enabling lockdown mode for this workflow since it processes issues from the public repo and we want to ensure it only processes trusted input from maintainers.
-    lockdown: true
     toolsets: [issues, labels]
 safe-outputs:
   add-labels: