Squelch ref-replication gerrit warnings

Change Ibbcc1009a47ae92ef7a364aee82509e1712d78d0 will add better
handling for replication events, but in the mean time, reduce
the chattiness of the gerrit-related log since we know there is
no account-related information for these events.

Change-Id: I491aafb038b7869c2ebc65c6225006ffb240c10e
1 file changed