[web] Use hook instead of connect function in InnerThreadEntity

Test Plan: Checked if the robotext would still show up, and other message types still worked normally

Reviewers: palys-swm, ashoat, atul

Reviewed By: ashoat

Subscribers: ashoat, KatPo, zrebcu411, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D838