Clarify that Stop terminates all ongoing requests (#3674)

Author: alnikola

xml/System.Net/HttpListener.xml

@@ -1164,7 +1164,7 @@ The following code example demonstrates calling the `Close` method:
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>Causes this instance to stop receiving incoming requests.</summary>
+        <summary>Causes this instance to stop receiving new incoming requests and terminates processing of all ongoing requests.</summary>
         <remarks>
           <format type="text/markdown"><![CDATA[