Bitrate must be at least 8000

per the following API error:
{
  "bitrate": [
    "Int value should be greater than 8000."
  ]
}

src/Discord.Net.Core/API/DiscordRestApiClient.cs

@@ -357,7 +357,7 @@ namespace Discord.API
         {
             Preconditions.NotEqual(channelId, 0, nameof(channelId));
             Preconditions.NotNull(args, nameof(args));
-            Preconditions.GreaterThan(args.Bitrate, 0, nameof(args.Bitrate));
+            Preconditions.GreaterThan(args.Bitrate, 8000, nameof(args.Bitrate));
             Preconditions.AtLeast(args.UserLimit, 0, nameof(args.Bitrate));
             Preconditions.AtLeast(args.Position, 0, nameof(args.Position));
             Preconditions.NotNullOrEmpty(args.Name, nameof(args.Name));