Fixed notebook by changing mcmc parameters

[zinaStef]

Fixed tutorial notebook 14 14_iid_data_and_permutation_invariant_embeddings, which was failing in cell 12.

The problem was that the sampler produced samples that had inf value (see issue #1060) and the pair_plot function was failing when computing the x-axis max limit based on the samples (see issue #1059). To solve it I changed the warmup parameter of the mcmc

mcmc_parameters = dict(
    num_chains=50,
    thin=5,
    warmup_steps=30, # before 10
    init_strategy="proposal",
)
mcmc_method = "slice_np_vectorized"

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