[iOS] Update xcode to point to new proto location

Summary:
Update xcode project to reference new protobuff files

https://linear.app/comm/issue/ENG-1231

Depends on D4994

Test Plan: iOS CI passes

Reviewers: atul, varun, abosh

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D4995