Remove vendored orchestrating-agent-relay skill

The skill is maintained in AgentWorkforce/skills
(skills/orchestrating-agent-relay); the copies under .claude/ and
.agents/ in relay were stale duplicates. Updated canonical version:
AgentWorkforce/skills#69.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: willwashburn