Fix remarks for Referer (#10910)

Fixes dotnet/runtime#31225

Retested the WebRequest, it does not auto-include the Referer header in any of the requests during redirect.

Author: ManickaP

xml/System.Net/HttpWebRequest.xml

@@ -4492,8 +4492,6 @@ The GetHashCode method returns a hash code of the web request. This value can be
 
 [!INCLUDE [obsolete-notice](~/includes/web-request-obsolete.md)]
 
- If the <xref:System.Net.HttpWebRequest.AllowAutoRedirect%2A> property is `true`, the <xref:System.Net.HttpWebRequest.Referer%2A> property is set automatically when the request is redirected to another site.
-
  To clear the `Referer` HTTP header, set the <xref:System.Net.HttpWebRequest.Referer%2A> property to `null`.
 
 > [!NOTE]