Update models to VRS 2.1.0-snapshot.2026-02.2

[korikuzma]

We'll be making a new minor release in VRS to pull in GKS-Core 1.1.0 changes. We may also have updates to VRS. We should update the Pydantic models to align with the spec

Snapshot Release: https://github.com/ga4gh/vrs/releases/tag/2.1.0-snapshot.2026-02.2