update 'koch ic' test command

koch.nim

@@ -558,9 +558,7 @@ proc icTest(args: string) =
   for fragment in content.split("#!EDIT!#"):
     let file = inp.replace(".nim", "_temp.nim")
     writeFile(file, fragment)
-    var cmd = nimExe & " cpp --ic:legacy -d:nimIcIntegrityChecks --listcmd "
-    if i == 0:
-      cmd.add "-f "
+    var cmd = nimExe & " ic --hint:Conf:off --warnings:off "
     cmd.add quoteShell(file)
     exec(cmd)
     inc i