Update pytables.py to include a more thorough description of the min_itemsize variable

[JoeDediop]

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

I am a student contributing for the first time, none of the additions were generated with AI and this PR description is not generated by AI.

I am addressing Issue 14601 where the current documentation for 'min_itemsize' is not thorough enough. It seems to me based on my research that the issue is that people treat it as though it counts characters instead of byte size for strings being input into a table.

I kept the additions simple to avoid any confusion and am open to suggestions on how I can improve this contribution. If there are any specific issues please point me to the location in your contribution guide so I can better understand any errors I might have made.

[jbrockmendel]

Let’s start with the CI failures. Can you address them?

[jbrockmendel]

@JoeDediop can you address the CI failures