Conflicting / missing information on enums

[BillyWM]

Issue Creation Checklist

[x] I have read the contribution guidelines

Issue Description

What was unclear/insufficient/not covered in the documentation

The docs, under "Other Data Types", don't mention that enums are Postgres only, but the API reference does. Since "Other Data Types" calls out a number of features that are dialect-specific, the omission of this info leads one to assume that enums are supported across all dialects (somehow)

If possible: Provide some suggestion on how we can enhance the docs

If enums are indeed only supported on Postgres, this information should be added to the Other Data Types page by changing the section header (consistent with e.g. "Ranges (PostgreSQL Only").

If enums work on all dialects, the incorrect note "An enumeration, Postgres Only "should be deleted from the API reference

Additional context

edit: This concerns v6. v7 has an appropriate notice.

[ephys]

The API reference is wrong here, enums are compatible with at least mariadb, mysql, and postgres. Not sure about the others. This PR sequelize/sequelize#14505 removed the mention (for v7)