Deprecate official support for vertica

[mfridman]

I'm not sure if the Vertica project is still maintained, and I cannot find any information on what happened to the Docker images for Vertica community edition. It appears they have been yanked from dockerhub:

https://hub.docker.com/r/vertica/vertica-ce

Originally added in: https://github.com/pressly/goose/pull/393

Note: official support within goose will be removed in /v4. Please do note that goose supports "custom stores", which means even if the core package doesn't have support, you can still implement the interface and use goose (which is what goose itself does).

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