[style] Named code-block elements show unnecessary block padding

[chalin]

For example, visit https://kubernetes.io/docs/concepts/scheduling-eviction/topology-spread-constraints/#topology-spread-constraint-examples and you'll currently see:

There shouldn't be whitespace around the grey code block -- i.e., the code block should extend to the border of it's parent container.

[dipesh-rawat]

/priority backlog /area web-development /triage accepted