Revert "Use property branch instead of the one from buildbucket."

This reverts commit fdc2d0f1835d9da93b315853984cc072d320332c.

Reason for revert: prod retries set git_ref and we should use git_url instead.

Original change's description:
> Use property branch instead of the one from buildbucket.
>
> This is to allow re-running tasks from production branches.
>
> Change-Id: I303bf44bd938c9a77bca2b8e4012b885dd230964
> Bug: https://github.com/flutter/flutter/issues/92127
> Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/19500
> Reviewed-by: Casey Hillers <chillers@google.com>
> Reviewed-by: Keyong Han <keyonghan@google.com>
> Commit-Queue: Godofredo Contreras <godofredoc@google.com>

TBR=godofredoc@google.com,keyonghan@google.com,chillers@google.com,flutter-scoped@luci-project-accounts.iam.gserviceaccount.com

Change-Id: Ia23769a88765ec380b78b39ecfa498860d9a0f69
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: https://github.com/flutter/flutter/issues/92127
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/19520
Reviewed-by: Godofredo Contreras <godofredoc@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>