[native] update copy for thread notification settings

Summary:
Breaking this task into multiple diffs becasue there are actually a lot of places that need to be changed + updated

Linear task: https://linear.app/comm/issue/ENG-8455/rename-focused-to-home-and-background-to-muted

Test Plan:
flow + confirmed that both the thread notif settings uis had the new copy

Reviewers: ashoat, inka

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12675