[web] Rename thread to chat
Summary:
Linear issue:
https://linear.app/comm/issue/ENG-1357/rename-sidebar-to-thread-in-product-copy
Diff renames thread to chat in all strings displayed to the user in web
Test Plan: Checked if strings changed as expected in web.
Reviewers: palys-swm, ashoat, def-au1t, yayabosh
Reviewed By: ashoat, yayabosh
Subscribers: Adrian, atul, yayabosh
Differential Revision: https://phab.comm.dev/D4539