[lib] modify rawThreadInfoFromServerThreadInfo to return default avatar to old clients

Summary:
this change means that when fetchThreadInfos is called with an old client as the viewer, the raw thread info will contain a null avatar

the min native and web versions were set to the same versions as fetchKnownUserInfos

Depends on D13746

Test Plan: fetched threads from old native client and got back default avatar for farcaster avatar threads

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13749