{Compute} Update doc of image-version

[qwordy]

Description

"<>" displays incorrectly in HTML. It is treated as a HTML tag.
Only at release time can I see the HTML page. This is the problem!

Plain text:

Space-separated list of customer managed keys for encrypting the OS and data disks in the gallery artifact for each region. Format for one region: “<os_des>,<lun1>,<lun1_des>,<lun2>,<lun2_des>”. Use "null" as a placeholder.

HTML page:

Testing Guide

History Notes

[Component Name 1] BREAKING CHANGE: az command a: Make some customer-facing breaking change.
[Component Name 2] az command b: Add some customer-facing feature.

---

This checklist is used to make sure that common guidelines for a pull request are followed.

• The PR title and description has followed the guideline in Submitting Pull Requests.

• I adhere to the Command Guidelines.

[jiasli]

I have a PR #13060 to fix all occurrences, but let's confirm with PM first whether we should backtick-quote them or docs team should escape <...>.

[qwordy]

I have a PR #13060 to fix all occurrences, but let's confirm with PM first whether we should backtick-quote them or docs team should escape <...>.

Docs team says it's Markdown.