Drop dependency on bob.io.matlab

Looks like bob.io.matlab is listed here but not used:

bob.bio.vein/requirements.txt
12:bob.io.matlab

bob.bio.vein/bob/bio/vein/tests/test.py
22:import bob.io.matlab

bob.bio.vein/develop.cfg
22:          src/bob.io.matlab
52:bob.io.matlab = git git@gitlab.idiap.ch:bob/bob.io.matlab

bob.bio.vein/matlab/compare.py
9:import bob.io.matlab

bob.bio.vein/conda/meta.yaml
39:    - bob.io.matlab

bob.io.matlab is deprecated bob.io.matlab#5 (closed)