Updates account referred_by field

Example response

{
  "is_username_private": true,
  "marketed_by": "maxDegen",
  "notifications": {
    "fill_sound": true,
    "fills": true,
    "orders": true,
    "transfers": true
  },
  "referral": {
    "commission_rate": "0.1",
    "commission_volume_cap": "1000000000",
    "discount_rate": "0.1",
    "discount_volume_cap": "30000000",
    "minimum_volume": "0.123",
    "name": "Referral",
    "points_bonus_rate": "0.1",
    "points_bonus_volume_cap": "1000000000",
    "referral_type": "Referral"
  },
  "referral_code": "cryptofox8",
  "referred_by": "maxDegen",
  "size_currency_display": "BASE",
  "tap_share_rate": {
    "last_updated_at": 1715592690488,
    "share_rate": "0.2"
  },
  "username": "username",
  "xp_share_rate": {
    "last_updated_at": 1715592690488,
    "share_rate": "0.2"
  }
}