docs: Removed dead link

[d3athjest3r]

This markdown page was removed from the wiki in 2021 by commit ab2555e0db60 (from: https://github.com/xcp-ng/xcp.wiki.git). So, remove the text referencing this page.

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• "I accept that my contribution is placed under the CC BY-SA 2.0 license [1]."
• "My contribution complies with the Developer Certificate of Origin [2]."

[1] https://creativecommons.org/licenses/by-sa/2.0/
[2] https://docs.xcp-ng.org/project/contributing/#developer-certificate-of-origin-dco