Don't use time-critical priority for VM thread

Fixes some unresponsiveness on Windows

src/qt/qt_main.cpp

@@ -441,9 +441,6 @@ main_thread_fn()
     int      frames;
 
     QThread::currentThread()->setPriority(QThread::HighestPriority);
-#ifdef _WIN32
-    SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);
-#endif
     plat_set_thread_name(nullptr, "main_thread_fn");
     framecountx = 0;
     // title_update = 1;