Update JsonExtensionDataAttribute.xml

Author: Ron Petrusha

xml/System.Text.Json.Serialization/JsonExtensionDataAttribute.xml

@@ -28,7 +28,7 @@
 
 The dictionary's `TKey` value must be <xref:System.String>, and `TValue` must be <xref:System.Text.Json.JsonElement> or <xref:System.Object>.
 
-During deserialization, when using <xref:System.Object>, a "null" JSON value is treated as a `null` object reference, and when using <xref:System.Text.Json.JsonElement>, a "null" is treated as a JsonElement with <xref:System.Text.Json.JsonElement.ValueKind> set to <xref:System.Text.Json.JsonValueKind.Null?displayProperty=nameWithType>.
+During deserialization, when using <xref:System.Object>, a "null" JSON value is treated as a `null` object reference, and when using <xref:System.Text.Json.JsonElement>, a "null" is treated as a JsonElement with <xref:System.Text.Json.JsonElement.Type> set to <xref:System.Text.Json.JsonValueType.Null?displayProperty=nameWithType>.
             
 During serialization, the name of the extension data property is not included in the JSON; the data contained within the extension data is serialized as properties of the JSON object.