MALA FlowMC sampler not working

[sachaguer]

There is a problem in the shape when using vmap on the unnormalized_log_prob function. MALA FlowMC not working now.
It could be useful to sample multimodal distributions.

[sachaguer]

New versions of FlowMC have been pushed leading to inconsistency with the current code. The code related to FlowMC has been commented in the meantime.