[web] Fix unread thread title styling in ChatThreadListItem

Summary: Title is correct color when unread: https://blob.sh/atul/664a.png

Test Plan: NA

Reviewers: def-au1t, palys-swm, varun, benschac

Reviewed By: palys-swm

Subscribers: ashoat, Adrian, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3359