[protos] Remove social_proof from IdentityKeyInfo
Summary:
Addresses ENG-7530.
Removed the already-unused social_proof field from IdentityKeyInfo proto message type.
Depends on D11548
Test Plan: Everything still compiles, commtest able to call login/registration and X3DH RPCs as before.
Reviewers: ashoat, varun
Reviewed By: ashoat, varun
Subscribers: kamil, tomek
Differential Revision: https://phab.comm.dev/D11549