[infra] Update the signing identity for iOS to a new, unexpired cert.

This ought to fix both the Mac and iOS builds and is needed as an addendum to
https://skia-review.googlesource.com/c/skia/+/531553.

Change-Id: Iddc1adc58284fdf4c38ea01486dec8963db55157
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/532779
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Erik Rose <erikrose@google.com>
3 files changed