[ios] Update Podfile.lock

Summary: ended up updating cocoapods via brew as part of investigating an Xcode issue, so just putting this up to keep my staging area clean

Test Plan: NA

Reviewers: ashoat, palys-swm

Reviewed By: ashoat

Subscribers: Adrian, karol-bisztyga, benschac

Differential Revision: https://phabricator.ashoat.com/D3484