This reverts commit 9be098b5.

Reason for revert: Fixed in the auto-rollers. They should now
include Bug: tags.

Original change's description:
> PRESUBMIT.py: Don't require "Bug:" for autoroller CLs.
> 
> BUG=angleproject:3659
> 
> Change-Id: I29d77939953e3661ea979f8f7a9f44566079e567
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1692881
> Commit-Queue: Jamie Madill <jmadill@chromium.org>
> Reviewed-by: Jamie Madill <jmadill@chromium.org>

TBR=geofflang@chromium.org,cwallez@chromium.org,jmadill@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: angleproject:3659
Change-Id: I01a2e82c24918c831a6c444360620d261ec892dc
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1700141Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>