[web][native] Fix message search showing toggle pin robotext

Summary:
issue: https://linear.app/comm/issue/ENG-4910/message-search-show-unpin-messages
This diff fixes toggle pin robotexts showing up in search results

Test Plan: checked that the robotext does not show up in search results, but the messages do.

Reviewers: rohan, michal

Reviewed By: rohan

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9126