Update an open channel

{
  "cover_url": "cover_url",
  "metadata": "{}",
  "data": "data",
  "custom_type": "custom_type",
  "is_ephemeral": true,
  "created_at": 0,
  "is_dynamic_partitioned": true,
  "channel_url": "channel_url",
  "freeze": true,
  "participant_count": 1,
  "operators": [
    {
      "metadata": "{}",
      "require_auth_for_profile_image": true,
      "is_active": true,
      "role": "",
      "user_id": "user_id",
      "profile_url": "profile_url",
      "nickname": "nickname",
      "is_blocked_by_me": true
    },
    {
      "metadata": "{}",
      "require_auth_for_profile_image": true,
      "is_active": true,
      "role": "",
      "user_id": "user_id",
      "profile_url": "profile_url",
      "nickname": "nickname",
      "is_blocked_by_me": true
    }
  ],
  "max_length_message": 6,
  "name": "name"
}