Apply suggestions from code review

Author: gewarren

xml/System.Xml.Linq/XAttribute.xml

@@ -3062,7 +3062,7 @@ Console.WriteLine(root)
 
  This example produces the following output:
 
-```txt
+```xml
 <Root Att1="content1" Att3="content3" />
 ```
 
@@ -3149,7 +3149,7 @@ Console.WriteLine(root)
 
  This example produces the following output:
 
-```txt
+```xml
 <Root Att1="content1" Att2="new content" Att3="content3" />
 ```
 

xml/System.Xml.Linq/XDocument.xml

@@ -731,7 +731,7 @@ Console.WriteLine(doc.Declaration)
 
  This example produces the following output:
 
-```txt
+```xml
 <?xml version="1.0" encoding="utf-8" standalone="yes"?>
 ```
 
@@ -1163,7 +1163,7 @@ Console.WriteLine(doc)
 
  This example produces the following output:
 
-```txt
+```xml
 <PurchaseOrder PurchaseOrderNumber="99503" OrderDate="1999-10-20">
   <Address Type="Shipping">
     <Name>Ellen Adams</Name>
@@ -3032,7 +3032,7 @@ Console.WriteLine(File.ReadAllText("Root2.xml"))
 
  This example produces the following output:
 
-```txt
+```xml
 <?xml version="1.0" encoding="utf-8"?><Root><Child>content</Child></Root>
 <?xml version="1.0" encoding="utf-8"?>
 <Root>

xml/System.Xml.Linq/XElement.xml

@@ -578,7 +578,7 @@ Console.WriteLine(xse)
 
  This example produces the following output:
 
-```txt
+```xml
 <NewRoot>
   <Child2>2</Child2>
   <Child3>3</Child3>

xml/System.Xml.Linq/XNamespace.xml

@@ -659,7 +659,7 @@ End Module
 
  This example produces the following output:
 
-```txt
+```xml
 <Root xmlns="http://www.adventure-works.com">
   <Child />
 </Root>
@@ -1056,7 +1056,7 @@ Console.WriteLine(root)
 
  This example produces the following output:
 
-```txt
+```xml
 <Root xml:space="preserve">
   <Child>content</Child>
 </Root>
@@ -1151,7 +1151,7 @@ End Module
 
  This example produces the following output:
 
-```txt
+```xml
 <aw:Root xmlns:aw="http://www.adventure-works.com">
   <aw:Child>content</aw:Child>
 </aw:Root>

xml/System.Xml.Linq/XProcessingInstruction.xml

@@ -185,7 +185,7 @@ Console.WriteLine(pi)
 
  This example produces the following output:
 
-```txt
+```xml
 <?xml-stylesheet type='text/xsl' href='hello.xsl'?>
 ```
 

xml/System.Xml.Linq/XStreamingElement.xml

@@ -593,7 +593,7 @@ Console.WriteLine(dstTree)
 
  This example produces the following output:
 
-```txt
+```xml
 <NewRoot>
   <DifferentChild>3</DifferentChild>
   <DifferentChild>4</DifferentChild>