Migrate UsersAvatarLink to standard Pajamas components

What does this MR do and why?

As a part of initiative to migrate UsersAvatarLink, we want migrate usages of UsersAvatarLink when it's easily replacable with standard elements.

Visual change:

Set the avatar size to 24 (closest number to the default 20) as it's the one supported by gl-avatar

Related to #355854 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the Feature Toggle for the imgration

   Feature.enable(:ci_pipeline_triggers_settings_vue_ui)

2. Open the project CI/CD settings of any project http://localhost:3000/flightjs/Flight/-/settings/ci_cd
3. Expand Pipeline triggers section
4. Click Add a trigger or observe already existing list in the table
5. Check the avatar is shown correctly and has a correct link

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.