fix: update broken visualization in the style guide, clean up headings to match other languages

[iennae]

Remove broken visual with

by removing alert Fix headings to match other languages should be 3 "#" not 4.
Clear up some confusing language.

Broken Visual for the Explanation

[github-actions[bot]]

🔎 Preview at https://GoogleCloudPlatform.github.io/samples-style-guide/previews/PR-120/

[iennae]

@grayside can you take a look?

[github-actions[bot]]

🔎 Preview at https://GoogleCloudPlatform.github.io/samples-style-guide/previews/PR-120/

[github-actions[bot]]

🔎 Preview at https://GoogleCloudPlatform.github.io/samples-style-guide/previews/PR-120/

[github-actions[bot]]

🧨 Preview deployments removed.