Deprecate Redis-Named Fields

[christhemorse]

Description

This PR brings the Terraform provider up to date with recent Govultr changes removing Redis-named fields and properties to replace them with generic versions. This is for future support of other caching engine types.

Checklist:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you linted your code locally prior to submission?
• Have you successfully ran tests with your changes locally?

[optik-aper]

Looks good