Service Desk list - fix link to documentation

What does this MR do and why?

• updates link to documentation, after it changed
• using injected path, rather than creating strings in each component

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

You can see the redirect to the right page on the before recording.

Before	After
before_change_with_redirect	after_change_without_redirect

How to set up and validate locally

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

SERVICE DESK SETUP

1. Setup a service desk on your GDK: https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/howto/service_desk_mail_room.md
2. Send an email to your Service Desk, so you have something to display on the list.

ALTERNATIVE SETUP

1. You can omit Service Desk setup and force an already existing issue to become a SD issue. Open the rails console: rails c
2. Use these commands. Change 7 to the project id that matches the one you want to use for testing:

email = 'your-email@gitlab.com'
project = Project.find 7
issue = project.issues.last
issue.update!(service_desk_reply_to: email, author: User.support_bot)
IssueEmailParticipant.create!(issue: issue, email: email)

1. In rails console enable the feature flag

   Feature.enable(:service_desk_vue_list)
   Feature.enable(:frontend_caching)

2. Visit the project that has Service Desk setup

3. In the main navigation click Monitor, than Service Desk.

4. Depending on the state of your Service Desk, you can find the link to documentation in either the empty state or the info banner above the issues list. Look for Learn more about Service Desk 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.

Related to #413092 (closed)