Remove Obsolete SentryUser.Segment

[jamescrosswell]

This is obsolete:

sentry-dotnet/src/Sentry/SentryUser.cs

Lines 85 to 89 in 2ef9f80

	/// <summary>
	/// The segment the user belongs to.
	/// </summary>
	[Obsolete("This property is deprecated and will be removed in a future version.")]
	public string? Segment

What should people do/use instead?