[lib] Add flow suppression to deprecatedMinimallyEncodeRawThreadInfo

Summary:
Add flow suppression to deprecatedMinimallyEncodeRawThreadInfo because it will only be called in contexts where member permissions do exist.

This function is only used in legacy migrations and in rawThreadInfoFromServerThreadInfo.

Depends on D12733

Test Plan: Close reading, there are no logic changes... just flow suppressions to account for differing representation of RawThreadInfo.members

Reviewers: ashoat, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D12755