fix config (#31883)

examples/window-app/silabs/openthread.gn

@@ -23,7 +23,7 @@ check_system_includes = true
 default_args = {
   target_cpu = "arm"
   target_os = "freertos"
-  chip_openthread_ftd = true
+  chip_openthread_ftd = false
 
   import("//openthread.gni")
 }