Add comment for force retrigger of Probe

Added a comment to indicate a force retrigger for Probe.

Author: MDA2AV

src/Servers/GenHttpServer/Program.cs

@@ -40,3 +40,5 @@ static string Echo(IRequest request)
 static string StringContent() => "OK";
 
 static Stream RequestContent(Stream body) => body;
+
+// force retrigger Probe