DOGM: Slow down touchscreen calibration (#20454)

Marlin/src/lcd/dogm/u8g_dev_tft_upscale_from_128x64.cpp

       lcd_put_u8str(0, LCD_PIXEL_HEIGHT / 2, str);
     } while (u8g.nextPage());
     drawing_screen = false;
+    safe_delay(250);
+    if (calibration_stage == CALIBRATION_SUCCESS) {
+      safe_delay(500);
+      ui.goto_previous_screen();
+    }
   }
 
 #endif // TOUCH_SCREEN_CALIBRATION