Fix FIXME about unecessary branching.
Fix FIXME about unecessary branching.

Older version of CrossCat maintained different internal state in X_L,
where the key ['row_partition_model']['hypers']['log_alpha'] existed.
The new key is ['row_partition_model']['hypers']['alpha'] so the
branch is never invoked.

probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,mit-probabilistic-computing-project/crosscat