docs: fix broken Markdown link (issue #10018)

[notlevi911]

Resolves #10018.

Description

What is the purpose of this pull request?

This pull request:

• Fixes broken Markdown link in the variancech README by replacing the non-functional DOI URL with the working ACM Digital Library URL for the Schubert & Gertz (2018) reference

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• resolves Fix broken Markdown link: https://doi.org/10.1145/3221664.3221674 #10018

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

---

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[Planeshifter]

The proposed fixed URL returns

Error 404
Page not found

[notlevi911]

should be working now, the doi itself was incorrect, thought changing the the domain from doi.org to dl.acm.org would work but turns out the actual correct DOI for the Schubert & Gertz 2018 paper is 10.1145/3221269.3223036