feat(aws_docdb_cluster): upgrade the default engine_version to 5.0.0

[gmeligio]

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what

Upgrade the default engine_version to the latest as of today, which is 5.0.0.

why

• To get the new features available and also the compatibility with MongoDB 5.0 API.
• To avoid the problems that come with edge cases when upgrading from 3.6/4.0 to 5.0, if we wanted 5.0 since the beginning but forgot to specify it.

references

• https://docs.aws.amazon.com/documentdb/latest/developerguide/compatibility.html#compatibility-whatsnew-5
• https://docs.aws.amazon.com/documentdb/latest/developerguide/docdb-mvu.html#mvu-prerequisites