SDK / exoplayer

While HDR is most closely tied to the color transfer (ex.
COLOR_TRANSFER_SDR is the only one explicitly mentioning dynamic
range), technically color spaces may be associated with HDR as well,
like BT.2020 commonly being used for HDR rather than BT.709 for SDR.

Therefore, it's more specific to mention just that the transfer is HDR.

PiperOrigin-RevId: 466316960
(cherry picked from commit 7075f78e)