Drop --token from the hand-started worker examples

The worker reads FLUKSIO_WORKER_TOKEN itself; on the command line the
token shows in ps. The --token row in the options table says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013GAeg4Jo6xjZzjwy9QDWMQ

docs/concepts/runs.md

@@ -270,7 +270,6 @@ pip install fluksio-worker
 
 fluksio-worker \
   --url wss://api.${DOMAIN}/api/v1/workers/attach \
-  --token "$FLUKSIO_WORKER_TOKEN" \
   --labels gpu,cuda12 \
   --python /opt/torch-venv/bin/python
 ```