all: use built-in max/min to simplify the code

all:  use built-in max/min to simplify the code

Change-Id: I309d93d6ebf0feb462217a344d5f02c190220752
Reviewed-on: https://go-review.googlesource.com/c/go/+/661737
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>