removed mentioning support for RestCategoryChannel, added channels property to SocketCategoryChannel

src/Discord.Net.Rest/Entities/Channels/RestCategoryChannel.cs

@@ -11,8 +11,6 @@ namespace Discord.Rest
     [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
     public class RestCategoryChannel : RestGuildChannel, ICategoryChannel
     {
-        public string Mention => MentionUtils.MentionChannel(Id);
-
         internal RestCategoryChannel(BaseDiscordClient discord, IGuild guild, ulong id)
             : base(discord, guild, id)
         {

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

@@ -17,6 +17,9 @@ namespace Discord.WebSocket
         public override IReadOnlyCollection<SocketGuildUser> Users
             => Guild.Users.Where(x => x.VoiceChannel?.Id == Id).ToImmutableArray();
 
+        public IReadOnlyCollection<SocketGuildChannel> Channels
+            => Guild.Channels.Where(x => x.CategoryId == CategoryId).ToImmutableArray();
+
         internal SocketCategoryChannel(DiscordSocketClient discord, ulong id, SocketGuild guild)
             : base(discord, id, guild)
         {