Remove deprecated BuildInfo.isAtLeastS() calls.

Replace most calls to BuildInfo.isAtLeastS() with direct checks of the
SDK version now that we build with the S SDK.

Change-Id: I1a8eec0204326ae323336155b5877ade5a412410
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3067500


Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: Will Cassella <cassew@google.com>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Reviewed-by: Shimi Zhang <ctzsm@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#908591}