Increase SDK builder bot_update timeout from 25 to 35 minutes

The download of clang and rbe from cipd is taking a little longer,
pushing the build step time from just under 25 minutes to just over.

Change-Id: I35d352fc5615f382b8f4bcce5d6ffd45aa084576
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/359066
Auto-Submit: William Hesse <whesse@google.com>
Reviewed-by: Kevin Chisholm <kevinjchisholm@google.com>
Commit-Queue: Kevin Chisholm <kevinjchisholm@google.com>
6 files changed