[pandas] Review recent pandas release notes

[mmcky]

It is a good idea to iterate on our pandas lectures by reviewing the recent release notes for pandas>=2.0.

https://pandas.pydata.org/docs/whatsnew/index.html

• [ ] update lecture and/or syntax
• [ ] highlight any new features that may be useful to readers
• [ ] review lectures that contain pandas code to see if we should make any updates.

[longye-tian]

Hi Matt @mmcky

There are nine lectures involving pandas, as follows; I will keep reviewing and posting updates following this comment.

• [ ] long_run_growth.md (Valid under new release, one issue related to plt.savefig. Please check the details in #467 )
• [ ] business_cycle.md
• [ ] inflation_history.md
• [ ] inequality.md
• [ ] prob_dist.md
• [ ] heavy_tails.md
• [ ] networks.md
• [x] simple_linear_regression.md (reviewed by @mmcky )
• [ ] mle.md

Best, Longye

[mmcky]

thanks @longye-tian this is great investigative work.