Use inherited Details implementation in RichGame

src/Discord.Net.Core/Entities/Activities/RichGame.cs

@@ -10,10 +10,6 @@ namespace Discord
     {
         internal RichGame() { }
 
-        /// <summary>
-        ///     Gets what the player is currently doing.
-        /// </summary>
-        public string Details { get; internal set; }
         /// <summary>
         ///     Gets the user's current party status.
         /// </summary>