fix: limit request members batch size

Discord is actually enforcing v8 limits on v6 according to https://github.com/discord/discord-api-docs/issues/2184

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -370,7 +370,7 @@ namespace Discord.WebSocket
         {
             var cachedGuilds = guilds.ToImmutableArray();
 
-            int batchSize = _gatewayIntents.HasValue ? 1 : 100;
+            const short batchSize = 1;
             ulong[] batchIds = new ulong[Math.Min(batchSize, cachedGuilds.Length)];
             Task[] batchTasks = new Task[batchIds.Length];
             int batchCount = (cachedGuilds.Length + (batchSize - 1)) / batchSize;