Revert "Use Rec 2020 colorspace for WCG support even if HDR is off on the host"

Rec 2020 conversion causes colors to be blown out in SDR

This reverts commit 472e8ee92e.

app/streaming/video/ffmpeg.cpp

@@ -87,9 +87,9 @@ int FFmpegVideoDecoder::getDecoderCapabilities()
     return capabilities;
 }
 
-int FFmpegVideoDecoder::getDecoderSdrColorspace()
+int FFmpegVideoDecoder::getDecoderColorspace()
 {
-    return m_FrontendRenderer->getDecoderSdrColorspace();
+    return m_FrontendRenderer->getDecoderColorspace();
 }
 
 int FFmpegVideoDecoder::getDecoderColorRange()