[MNG-7893] Fix exception loading superpom with invalid modelVersion

[gnodet]

Even though this should not be supported, Maven 3.x is always using the 4.0.0 superpom. So if the version is not a supported model version, simply use 4.0.0. Any invalid value will be later verified by the model validator and eventually throw a meaninfual exception.

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[jira-importer]

Resolve #9028