Inconsistency between property type and its comment in IGuild.PremiumSubscriptionCount

[gehongyan]

Around IGuild.PremiumSubscriptionCount.

The type is int, but it is commented that <see langword="null" /> if not available.

I am not sure which is better to change the type to int? or Optional<int>, or to edit the comment. Hence the opening of this issue.

https://github.com/discord-net/Discord.Net/blob/dev/src/Discord.Net.Core/Entities/Guilds/IGuild.cs#L272-L274