Deprecate in favor of UUIDv7

[booch]

I just read about UUIDv7. It's a proposed IETF standard, in "last call". Other than the base32 encoding, it's got everything we want from ULID. UUIDv7 will be more widely accepted and available to developers.

I propose that we declare victory, and allow the UUID spec to take over the effort from here on.