Revert some thread priority level changes

src/GameLoop.cpp

@@ -24,10 +24,6 @@
 #include <cmath>
 #include <vector>
 
-#ifdef _WIN32
-#include "archutils/Win32/ThreadPriorityHelper.h"
-#endif
-
 static RageTimer g_GameplayTimer;
 
 static Preference<bool> g_bNeverBoostAppPriority( "NeverBoostAppPriority", false );
@@ -413,13 +409,6 @@ void ConcurrentRenderer::RenderThread()
 
 		if( m_State == RENDERING_START )
 		{
-#ifdef _WIN32
-			bool setThreadSuccess = BoostThreadPriorityToHighest();
-			if (!setThreadSuccess)
-			{
-				ASSERT_M(0, "Failed to set thread priority to highest.");
-			}
-#endif
 			/* We're starting to render. Set up, and then kick the event to wake
 			 * up the calling thread. */
 			DISPLAY->BeginConcurrentRendering();