363 example tensor for cp als needs to have cp structure

[dmdunla]

@tgkolda Can you review this PR, which addresses #363 ?

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📚 Documentation preview 📚: https://pyttb--392.org.readthedocs.build/en/392/

[dmdunla]

Note that this only changes the tutorial for cp_als. Once this looks good, we should make changes for other algorithms to use low-rank tensors as input. Currently, the tutorials were aimed at replication of the MATLAB TTB tutorials, except that loaded data was replaced with generated data. So, this should be revisited to improve consistency across the tutorials.

[tgkolda]

Hi @dmdunla, This is a bad example because it takes too long to converge. Using normal random values rather than uniform for factor matrices accelerates the convergence and should obviate the need to the limit of iterations.