Add missing VoiceServerUpdated event (#1089)

src/Discord.Net.WebSocket/DiscordShardedClient.cs

@@ -309,6 +309,7 @@ namespace Discord.WebSocket
             client.UserUpdated += (oldUser, newUser) => _userUpdatedEvent.InvokeAsync(oldUser, newUser);
             client.GuildMemberUpdated += (oldUser, newUser) => _guildMemberUpdatedEvent.InvokeAsync(oldUser, newUser);
             client.UserVoiceStateUpdated += (user, oldVoiceState, newVoiceState) => _userVoiceStateUpdatedEvent.InvokeAsync(user, oldVoiceState, newVoiceState);
+            client.VoiceServerUpdated += (server) => _voiceServerUpdatedEvent.InvokeAsync(server);
             client.CurrentUserUpdated += (oldUser, newUser) => _selfUpdatedEvent.InvokeAsync(oldUser, newUser);
             client.UserIsTyping += (oldUser, newUser) => _userIsTypingEvent.InvokeAsync(oldUser, newUser);
             client.RecipientAdded += (user) => _recipientAddedEvent.InvokeAsync(user);