qtdemux: fix wrong full_range offset when parsing colr box
use colr_data[18] >> 7 to get full range information, instead of colr_data[17] >> 7
following hex code is a colr box example, the offset of 0x80 is 18
00 00 00 13 63 6F 6C 72 6E 63 6C 78 00 01 00 01 00 00 80