Fix JsonIgnoreCondition.WhenWritingNull doc

[lilinus]

Doc only

It acutally applies to nullable value types too

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

Forecast forecast = new()
{
    Date = null,
};
JsonSerializerOptions options = new()
{
    DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
};
string forecastJson = JsonSerializer.Serialize<Forecast>(forecast, options);
Console.WriteLine(forecastJson); // Prints "{}"

public class Forecast
{
    public DateTime? Date { get; set; }
};

Should I manually make PR to https://github.com/dotnet/docs ?

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[eiriktsarpalis]

Why not keep simple?

Suggested change

	/// This is applied only to reference and nullable value-type properties and fields.
	/// This is applied only to nullable type properties and fields.

[lilinus]

Sounds good, unless it can be misinterpreted as not applied to non-nullable reference types in context. WDYT?