[Geomagic] Fix compilation. Replace Vector3 by Vec3

[epernod]

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Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[epernod]

the ci does not compile this plugin in any case so I guess it is ready 😅

trust me 🙈