update(platform/rtthread): remove unused idle task check

platform/rtthread/usb_check.c

@@ -6,10 +6,6 @@
 #error must enable RT_USING_TIMER_SOFT to support timer callback in thread
 #endif
 
-#if IDLE_THREAD_STACK_SIZE < 2048
-#error "IDLE_THREAD_STACK_SIZE must be >= 2048"
-#endif
-
 #if RT_TIMER_THREAD_STACK_SIZE < 2048
 #error "RT_TIMER_THREAD_STACK_SIZE must be >= 2048"
 #endif