vo_gpu_next: don't render ASS subtitles at HDR colorspace

Upstream ASS specification says that all subtitles should be rendered
with color primaries and transfer matching their associated video. But
as expected after further discussion the decision has been made to
fallback to SDR mode in case of HDR video.

See-Also: https://github.com/libass/libass/blob/649a7c2e1fc6f4188ea1a89968560715800b883d/libass/ass_types.h#L233-L237
See-Also: libass/libass#297
See-Also: #13381
Fixes: #13673

video/out/vo_gpu_next.c

@@ -379,7 +379,7 @@ static void update_overlays(struct vo *vo, struct mp_osd_res res,
             }
             break;
         case SUBBITMAP_LIBASS:
-            if (src && item->video_color_space)
+            if (src && item->video_color_space && !pl_color_space_is_hdr(&src->params.color))
                 ol->color = src->params.color;
             ol->mode = PL_OVERLAY_MONOCHROME;
             ol->repr.alpha = PL_ALPHA_INDEPENDENT;