This reverts commit 31a538a3.

Reason for revert:
Breaks ANGLE's workflow.

Original change's description:
> git-cl: turn GERRIT_SQUASH_UPLOADS into a warning
> 
> Now that repos have dropped this from their codereview.settings file,
> change this logic to issue a warning if it's ever seen again.
> 
> Drop checking local gerrit.override-squash-uploads config too since
> it's no longer relevant.
> 
> Bug: 993518
> Change-Id: Id91bbc94b0890ca21c51a274f6acc41f2ae19b78
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1756159
> Commit-Queue: Mike Frysinger <vapier@chromium.org>
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>

TBR=vapier@chromium.org,ehmaldonado@chromium.org,infra-scoped@luci-project-accounts.iam.gserviceaccount.com

Change-Id: Iaa8b3341b189f356082ae25a1557898e25820566
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 993518
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2182019Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>