Make LRSM/mlrsm-nu-loop python3 compatible
Following the MR!219 and MR!221, the mlrsm-nu-loop model somehow passed the python3 compatibility test. I did not realise this until official MC signal production, since I still used the local converted model for the tests.
I now did a convert model mlrsm-nu-loop inside the mg5 on the atlas-models/LRSM/mlrsm-nu-loop, producing minimal differences that I would like to merge.
Thanks, Blaž