Reduce code duplication in renderers

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

@@ -278,11 +278,6 @@ public:
         return true;
     }
 
-    virtual int getDecoderCapabilities() override
-    {
-        return 0;
-    }
-
     virtual IFFmpegRenderer::FramePacingConstraint getFramePacingConstraint() override
     {
         // This renderer is inherently tied to V-sync due how we're
@@ -291,12 +286,6 @@ public:
         return PACING_FORCE_ON;
     }
 
-    virtual bool isRenderThreadSupported() override
-    {
-        // renderFrame() may be called outside of the main thread
-        return true;
-    }
-
 private:
     AVBufferRef* m_HwContext;
     AVSampleBufferDisplayLayer* m_DisplayLayer;