Remove rich presence button

src/Discord.Net.Rest/API/Common/RichPresenceButton.cs

@@ -1,18 +0,0 @@
-using Newtonsoft.Json;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace Discord.API
-{
-    internal class RichPresenceButton
-    {
-        [JsonProperty("label")]
-        public string Label { get; set; }
-
-        [JsonProperty("url")]
-        public string Url { get; set; }
-    }
-}