Also replace the other thread sleep with play_delay_ms() and remove the #ifdef's.

src/qt/qt_main.cpp

@@ -149,12 +149,8 @@ main_thread_fn()
             if (dopause)
                 ack_pause();
 
-#ifdef USE_THREAD_SLEEP
-            std::this_thread::sleep_for(std::chrono::milliseconds(1));
-#else
             timeBeginPeriod(1);
             plat_delay_ms(1);
-#endif
         }
     }
 
@@ -162,7 +158,8 @@ main_thread_fn()
     for (uint8_t i = 1; i < GFXCARD_MAX; i ++) {
         if (gfxcard[i]) {
             ui_deinit_monitor(i);
-            std::this_thread::sleep_for(std::chrono::milliseconds(500));
+            timeBeginPeriod(1);
+            plat_delay_ms(500);
         }
     }
     QTimer::singleShot(0, QApplication::instance(), []() { QApplication::processEvents(); QApplication::instance()->quit(); });