DOC: remove sample_plots from tutorials

[jklymak]

PR Summary

Removes https://matplotlib.org/devdocs/tutorials/introductory/sample_plots.html#sphx-glr-tutorials-introductory-sample-plots-py and redirects it to https://matplotlib.org/devdocs/plot_types/index.html I think most of the info is redundant.

PR Checklist

Tests and Styling

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).

[dstansby]

I agree that the removed page is redundant - not fully covered by the page it's redirected from, but there's plenty of other stuff in the example gallery for what's missed.

[timhoffm]

I agree that the intent of sample_plots is better served by plot_types.