Fixing histogram test

Here you are always doubling the number of rows in the subplot (https://gitlab.idiap.ch/bob/bob.measure/blob/7c524a4f52bb0487177f602dbf0e25b7169015a6/bob/measure/script/figure.py#L818). Hence, this test should be like this:

./bin/bob measure hist -e -sp 121 -ts A,B,C,D ./bob/measure/data/dev-1.txt ./bob/measure/data/test-1.txt ./bob/measure/data/dev-2.txt ./bob/measure/data/test-2.txt

I think this will solve the issue with the nightlies

Closes #57 (closed)