Use lg variant for doc chevron

What does this MR do and why?

A small MVC to update a handful of chevron icons in the documentation to use the lg variant.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Relates to #362780 (closed), #362776 (closed), #362781 (closed)