It was not removed, it was converted to a fileID instead back in I believe Legion. Then, Shadowlands converted the function to return a table. The fileID is under the key "iconFileID".
https://wow.gamepedia.com/API_C_Curr...etCurrencyInfo
The following code will print "You have ## of Soul Ash" in chat with the Soul Ash icon right before the name.
Lua Code:
local data = C_CurrencyInfo.GetCurrencyInfo(1828)
if data.name and tonumber(data.quantity) then
local color = data.quality and ITEM_QUALITY_COLORS[data.quality].hex or ""
local message = "You have " .. data.quantity .. " of " .. (data.iconFileID and "|T"..data.iconFileID..":12|t" or "") .. color .. data.name .. "|r"
DEFAULT_CHAT_FRAME:AddMessage(message)
end