Change XML Encryption 1.1 to XML Encryption 1.0 (#5022)

The identifier http://www.w3.org/2009/ is not present at all in the code base. Which indicates the absence of any implementation of XML Encryption 1.1.
See discussion: dotnet/runtime#43436 (comment)

Author: dhcgn

xml/System.Security.Cryptography.Xml/EncryptedXml.xml

@@ -28,7 +28,7 @@
       <format type="text/markdown"><![CDATA[  
   
 ## Remarks  
- The <xref:System.Security.Cryptography.Xml.EncryptedXml> class is the main class used for XML encryption in the .NET Framework. XML Encryption is a standards-based, interoperable way to encrypt all or part of an XML document or any arbitrary data. The .NET Framework XML encryption classes implement the World Wide Web Consortium (W3C) [XML Encryption Syntax and Processing Version 1.1](https://www.w3.org/TR/xmlenc-core/) specification.  
+ The <xref:System.Security.Cryptography.Xml.EncryptedXml> class is the main class used for XML encryption in the .NET Framework. XML Encryption is a standards-based, interoperable way to encrypt all or part of an XML document or any arbitrary data. The .NET Framework XML encryption classes implement the World Wide Web Consortium (W3C) [XML Encryption Syntax and Processing Version 1.0](https://www.w3.org/TR/2002/REC-xmlenc-core-20021210/) specification.  
   
  Use the <xref:System.Security.Cryptography.Xml.EncryptedXml> class whenever you need to share encrypted XML data between applications or organizations in a standard way. Any data encrypted using this class can be decrypted by any implementation of the W3C specification for XML encryption.