Don't use CAMetalDisplayLink on Intel Macs

When in Direct mode, skipping a frame will cause the display to flash black on Tahoe.

app/streaming/video/ffmpeg-renderers/vt.h

@@ -12,6 +12,8 @@ public:
     void setHdrMode(bool enabled) override;
 
 protected:
+    bool isAppleSilicon();
+
     bool m_HdrMetadataChanged; // Manual reset
     CFDataRef m_MasteringDisplayColorVolume;
     CFDataRef m_ContentLightLevelInfo;