[lib] Fix TUnion/TInterface imports

Summary:
To fix following issue: https://blob.sh/dbc687.png

when running yarn dev in keyserver.

Thanks @ginsu for catching this.

Test Plan: Able to run yarn dev in keyserver without issue.

Reviewers: ashoat, ginsu

Reviewed By: ginsu

Subscribers: tomek, ginsu

Differential Revision: https://phab.comm.dev/D7111