[native] [web] Improve wording when clearing thread name or description

Summary:
Related Linear issue with full context here. Improved the wording of the robotext that is outputted when setting the thread name or description to the empty string.

Before:

After:

Test Plan:
Looks as expected on web and native, also changed thread name and description on web and native and both platforms match/work as expected:

Also tested to make sure the notification text matches the updated robotext (thanks @palys-swm for your help here!):

Reviewers: atul, palys-swm, ashoat

Reviewed By: atul, palys-swm, ashoat

Subscribers: ashoat, Adrian, palys-swm

Differential Revision: https://phab.comm.dev/D4346