This reverts commit 6651fd88.

Reason for revert: broke some cros builds (check original CL for
discussion)

Original change's description:
> Use HEAD instead of hardcoded branch
>
> Repositories may have different default branches. This ensures to fetch
> remote HEAD branch which is default branch. Only downside to this
> approach is that actual branch (e.g. origin/main) reference won't be
> updated. Since we don't need it for this particular case, it should be
> fine to use HEAD.
>
> R=​apolito@google.com, ehmaldonaldo@chromium.org
>
> Bug: 1155492
> Recipe-Nontrivial-Roll: chromiumos
> Recipe-Nontrivial-Roll: infra
> Recipe-Nontrivial-Roll: build_limited_scripts_slave
> Change-Id: Ib2e6e50901a0a10ed647acea3aeb517b83567702
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2580190
> Reviewed-by: Anthony Polito <apolito@google.com>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

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

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

Bug: 1155492
Recipe-Nontrivial-Roll: chromiumos
Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Recipe-Nontrivial-Roll: build
Change-Id: Ibd9f67bea71ee4a644b1077a365dbcd2a2c469f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2597065Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>