Update plantumlCheck to handle special case for windows

[tlylt]

Please confirm that you have searched existing issues in the repo

Yes, I have searched the existing issues

Any related issues?

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Tell us about your environment

Windows 10

MarkBind version

Master branch

Describe the bug and the steps to reproduce it

With the plantuml bump, we shouldn't need Graphviz on Windows. Hence we should update the check https://markbind-master.netlify.app/userguide/sitejsonfile#plantumlcheck accordingly, and update the related docs to handle this difference.

Expected behavior

No response

Anything else?

No response

[tlylt]

Hi @jmestxr feel free to help look into this issue if you are available. Should be an easy update that will remove the unwanted warning for good.