HttpListener.IsSupported always returns true (#4072)

* HttpListener.IsSupported always returns true

* Apply suggestions from code review

Co-Authored-By: Genevieve Warren <[email protected]>

Author: nxtn

xml/System.Net/HttpListener.xml

@@ -965,15 +965,10 @@ The following code example demonstrates calling the `Close` method:
       <Docs>
         <summary>Gets a value that indicates whether <see cref="T:System.Net.HttpListener" /> can be used with the current operating system.</summary>
         <value>
-          <see langword="true" /> if <see cref="T:System.Net.HttpListener" /> is supported; otherwise, <see langword="false" />.</value>
+          <see langword="true" /> on all platforms.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[  
   
-## Remarks  
- This class is available only on computers running the Windows XP SP2 or Windows Server 2003 operating systems.  
-  
-   
-  
 ## Examples  
  The following code example demonstrates the use of the <xref:System.Net.HttpListener.IsSupported%2A> property to detect whether an <xref:System.Net.HttpListener> object can be used with the current operating system.