Wrong property being used for Channels property

CategoryId is the category that "owns" this channel. That is actually impossible right now for category channels, so it returns null and get all channels wrongly.

src/Discord.Net.WebSocket/Entities/Channels/SocketCategoryChannel.cs

@@ -18,7 +18,7 @@ namespace Discord.WebSocket
             => throw new NotSupportedException();
 
         public IReadOnlyCollection<SocketGuildChannel> Channels
-            => Guild.Channels.Where(x => x.CategoryId == CategoryId).ToImmutableArray();
+            => Guild.Channels.Where(x => x.CategoryId == Id).ToImmutableArray();
 
         internal SocketCategoryChannel(DiscordSocketClient discord, ulong id, SocketGuild guild)
             : base(discord, id, guild)