1. Do not call matplotlib.use("svg") in the svg-specific examples, as
   this is unneeded (matplotlib will internally switch the canvas at save
   time) and triggers a warning because s-g already set the canvas to agg.

2. Do not report computation times for examples than ran faster than 1s
   (i.e., most of them) -- for fast examples, we are timing and reporting
   noise.

3. Some markup fixes.

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way