[Sync] Adapt PRESUBMIT to a change in sync.proto

The problem came with CL
https://chromium-review.googlesource.com/c/chromium/src/+/1129140.

Bug: 866876
Change-Id: I00c6a6464b6cd8a879c0c7bb72c03bc221137043
Reviewed-on: https://chromium-review.googlesource.com/1148388
Reviewed-by: Mohamed Amir Yosef <[email protected]>
Commit-Queue: Jan Krcal <[email protected]>
Cr-Commit-Position: refs/heads/master@{#577585}
2 files changed