[native] Block TimeStamp from rendering in the pinned messages screen

Summary:
As mentioned in ENG-3959, the TimeStamp renders through the MessageHeader in screens that are not MessageList, causing it to be blocked off by the header.

Based on the designs, we shouldn't render this in the first place.

Test Plan:
Confirm that timestamps still show in chat, but don't display onPress in the MessageResultsScreen.

Reviewers: kuba, ginsu

Reviewed By: kuba, ginsu

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8098