This reverts commit 2ec46bec.

Reason for revert:
avx2 builders have moved to the chromium swarming pool

Original change's description:
> [CQ] Temporarily make avx2 trybot experimental.
> 
> NOTRY=true
> NOPRESUBMIT=true
> TBR=tandrii@chromium.org
> 
> Bug: chromium:736757
> Change-Id: I920eda5c916981d3588fb7346ec4e811dc5112aa
> Reviewed-on: https://chromium-review.googlesource.com/548360
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Commit-Queue: Michael Achenbach <machenbach@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#46219}

TBR=machenbach@chromium.org,tandrii@chromium.org,clemensh@chromium.org

Change-Id: If228a34be2e6e88dbd2cc3fc1de0b227c4d113c2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:736757
Reviewed-on: https://chromium-review.googlesource.com/549321Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46236}