[autofill] Remove expires-after for ongoing histograms

This CL removes expires-after="M73" for the following histograms:

	Autofill.Query.BackoffDelay
	Autofill.Query.HttpResponseOrErrorCode
	Autofill.Query.RequestDuration

These histograms continue, and will continue, to be of value and should
not expire. In particular, these histograms will be of use when comparing
the autofill canary server environment users with the prod environment
control group.

Bug: 915896
Change-Id: Icf9845bc24c2e3cbf5f80ce453c7ff234c5ba756
Reviewed-on: https://chromium-review.googlesource.com/c/1394790
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Roger McFarlane <rogerm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619971}
1 file changed