docs(expel): rename INSTANCE_NAME -> INSTANCE_UUID

Summary

• docs(expel): rename INSTANCE_NAME -> INSTANCE_UUID

Address changes from picodata@c40d2629

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• Close #390 (closed)
• Cherry-pick to: none
• Staging:
  • ../reference/cli/#expel
  • ../architecture/rpc_api/#proc_expel
  • ../architecture/rpc_api/#proc_expel_redirect