Fixed unused timeout const, dropped default request timeout to 15s.

src/Discord.Net.Core/DiscordConfig.cs

@@ -14,6 +14,7 @@ namespace Discord
         public const string CDNUrl = "https://discordcdn.com/";
         public const string InviteUrl = "https://discord.gg/";
 
+        public const int DefaultRequestTimeout = 15000;
         public const int MaxMessageSize = 2000;
         public const int MaxMessagesPerBatch = 100;
         public const int MaxUsersPerBatch = 1000;

src/Discord.Net.Core/RequestOptions.cs

@@ -22,7 +22,7 @@
 
         public RequestOptions()
         {
-            Timeout = 30000;
+            Timeout = DiscordConfig.DefaultRequestTimeout;
         }
 
         public RequestOptions Clone() => MemberwiseClone() as RequestOptions;