Unpin numpy

[ntjohnson1]

Unpin numpy fixes #325

• Update pretty print for sptenmat and tenmat
• Minor other formatting fixes in doc tests

Also updates our ktensor vis:

• Makes the returns match subplots so users can manipulate figure and axes in down stream usage
• Use the updated interface to automatically generate the opened figures in doctests (for me locally the doctest hang until the figures are closed)

I think this also finished removing 3.8 support.

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📚 Documentation preview 📚: https://pyttb--329.org.readthedocs.build/en/329/