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

README.md

@@ -43,7 +43,7 @@ A machine that should only *run nodes* for an engine elsewhere installs less:
 
 ```sh
 pip install fluksio-worker
-fluksio-worker --url wss://api.fluksio.com/api/v1/workers/attach --token "$TOKEN" --labels gpu
+FLUKSIO_WORKER_TOKEN=… fluksio-worker --url wss://api.fluksio.com/api/v1/workers/attach --labels gpu
 ```
 
 ## Getting started