Migrate alert docs icon

What does this MR do and why?

A small MVC for Migrate angle icon to chevron in doc/operations... (#362777 - closed) where we migrate the angle icon to chevron in doc/operations/incident_management/alerts.md

Screenshots or screen recordings

Before	After

How to set up and validate locally

N/A

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.

Closes #362777 (closed)