[lib] Use tUserID in message-validators.js

Summary: issue: ENG-7819

Test Plan:
flow
tested that fetch_messages endpoint which uses fetchMessageInfosResponseValidator which uses userInfosValidator works correctly and doesn't throw

Reviewers: tomek, kamil, bartek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11964