[web] Rename replyTooltip to replyButton

Summary: Part of refactoring done with tooltipMenu introduction: reply is not a tooltip, but rather button

Test Plan: Flow, check if reply is still possible

Reviewers: palys-swm, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, palys-swm, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D992