Fix broken Linux command-line guide link

[dlanov]

Summary

This PR improves the Linux command-line prerequisite in the Creating a Workspace tutorial.

Based on maintainer feedback, the existing SFU Unix/Linux guide is retained and the Ubuntu beginner command-line guide is added as an alternative.

Changes

• Keeps the existing SFU Unix/Linux command-line guide.
• Adds Ubuntu's Linux command-line beginner guide as an alternative.
• Presents both resources as choices under the terminal-command prerequisite.

Testing

I ran:

• make html
• make lint
• make spellcheck
• git diff --check

The documentation build succeeded, lint reported no problems, spellcheck passed, and git diff --check returned no issues.

Part of #4209.

AI assistance disclosure

I used Claude Code to help prepare the documentation change, then manually reviewed the diff and test results before submitting.

[dlanov]

I updated the replacement link to use the newer Ubuntu Desktop documentation URL.

I re-ran:

• make html
• make lint
• make spellcheck
• curl -I https://ubuntu.com/desktop/docs/en/latest/tutorial/the-linux-command-line-for-beginners/

[fujitatomoya]

https://www2.cs.sfu.ca/~ggbaker/reference/unix/ seems working with no problems for me, what is the problem on this site? and this PR needs rebase.

[sloretz]

Thank you for the PR!

• Please resolve the merge conflict
• It looks like the existing link works, but I think we don't have much of an opinion on who teaches someone about the linux command line. Would you be willing to turn this into a bulleted list with both links? That way if one goes down, the reader can choose the other one.

[ahcorde]

friendly ping @dlanov

[dlanov]

Thanks for the ping, and sorry I missed the earlier feedback. I'll rebase the branch, resolve the conflict, and update the prerequisite to keep both the existing SFU guide and the Ubuntu command-line guide as alternatives.

[dlanov]

Thanks for the feedback. I've rebased the branch onto the latest rolling and updated the prerequisite to keep both the existing SFU guide and the Ubuntu guide as alternatives. I also re-ran the HTML build, lint, spellcheck, and diff checks.