Construct local badge-only notif when notification doesn't have body property
Summary: This differential solves the issue: https://linear.app/comm/issue/ENG-7773/badgeonly-notifs-on-ios-show-encrypted-notif-for-staff-members#comment-ac7ea6b6.
Test Plan:
- Build iOS app.
- Make a thread badge only.
- Sent notif to this thread.
- Ensure that badge is updated and no "ENCRYPTED" notifs are displayed.
Reviewers: ashoat, tomek, bartek
Reviewed By: ashoat
Differential Revision: https://phab.comm.dev/D11684