Update link to Web updates in fetch deprecation message

This change updates the developer facing deprecation message to link to
"Latest Updates to the Credential Management API" update post on
https://developers.google.com.

Bug: 718416
Change-Id: I1b190f5f66e8ed854d193ee6dc3af28e50d2c310
Reviewed-on: https://chromium-review.googlesource.com/535613
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: jdoerrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#479377}
2 files changed