[web][native] hide media gallery for thick threads

Summary:
ENG-9315.

Hiding media gallery for thick threads.

Test Plan:

1. On web and native this in not possible to access/see media gallery for thick threads.
2. For thin threads it works as previously.

Reviewers: tomek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13448