Update lines_with_ticks_demo.py

[ruthgn]

PR Summary

Add explanatory comments to the example on creating lines with ticked patheffect. PR related to issue #11654.

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).

[jklymak]

I think this example already has a enough explanation. I don't agree that we need to tell a user that ax.plot([0, 1], [0, 1]... will plot a straight line, or that sin(x) is a "curved line".

[dstansby]

I don't think the comments detract from the example, and having a bit more structuring helps. I think the example could be improved/expanded, but that can be for another PR Thanks for this PR!