qtdemux: add depth for ProRes 4:4:4:4 variants if available
Might be 24bpp in case an alpha channel is coded but the image is always opaque. Part-of: <gstreamer/gst-plugins-good!1062>
Might be 24bpp in case an alpha channel is coded but the image is always opaque. Part-of: <gstreamer/gst-plugins-good!1062>