The default value of XmlArrayAttribute.IsNullable is not stated.

The default value should be given. Other documentation states the default value for booleans. According to the source in Visual Studio (and the beviour I see) it should be false.

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* ID: 0cdd37be-116a-8dd5-41c5-88e1b73eb725
* Version Independent ID: 14ae5140-6542-cee7-8405-2e9c4fe49979
* Content: [XmlArrayAttribute.IsNullable Property (System.Xml.Serialization)](https://docs.microsoft.com/en-us/dotnet/api/system.xml.serialization.xmlarrayattribute.isnullable?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DEN-US%26k%3Dk(System.Xml.Serialization.XmlArrayAttribute.IsNullable);k(SolutionItemsProject);k(SolutionItemsProject);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.5);k(DevLang-csharp)%26rd%3Dtrue&view=netframework-4.7.2)
* Content Source: [xml/System.Xml.Serialization/XmlArrayAttribute.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Xml.Serialization/XmlArrayAttribute.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**