[Signin] Use `const GoogleServiceAuthError&` in
`OAuth2AccessTokenManager::DiagnosticsObserver::OnFetchAccessTokenComplete`

Requested on CL https://crrev.com/c/5563164

Bug: b/321900823
Change-Id: Icbc2a699cbcd2f68fd80b3c9d902c143edc0c4cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5642637
Reviewed-by: David Roger <droger@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Monica Basta <msalama@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1317249}
NOKEYCHECK=True
GitOrigin-RevId: 9f9c5a8c74643937edb485e29eae556770011c1e
2 files changed