DOC add vector field in MSA example

[MatthewSZhang]

Checklist

• Used a personal fork to propose changes
• A reference to a related issue: DOC add vector field in phase portraits of MSA NARX example #147
• A description of the changes: use streamplot to plot the vector field of Duffing equation

[MatthewSZhang]

fetch_openml does not work due to maintenance work from November 24-28 in OpenML. See
https://github.com/orgs/openml/discussions/27

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (122d00f) to head (98da52b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #206   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           10        10           
  Lines          704       704           
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  Hits           704       704           

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