[3.0] demux: mkv: allow reading v3 and v4 files
There's no requirement in v3 and v4 that we don't support. v5 doesn't exist yet.
Ref. #26999
(cherry picked from commit 6fd29e31)
Signed-off-by: Steve Lhomme robux4@ycbcr.xyz
Edited by Steve Lhomme