fix dead links around the site

[Recxsmacx]

Fixes #14823

Fix dead links in various markdown files.

• Replace dead link in public/content/dao/index.md with a working link to CityDAO.
• Replace dead link in public/content/defi/index.md with a working link to Aave.
• Replace dead link in public/content/enterprise/index.md with a working link to Coindesk.
• Replace dead link in public/content/wrapped-eth/index.md with a working link to WETH.

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[Recxsmacx]

@pettinarip @corwintines @wackerow @minimalsm please review this!

[github-actions[bot]]

This issue is stale because it has been open 30 days with no activity.

[wackerow]

Given changes and inconsistencies here, closing this one out