[cbuild] Remove support for legacy results

Change-Id: I506faad9b355265a5514c5db2265bd13d7161061
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/178780
Auto-Submit: Alexander Thomas <athom@google.com>
Reviewed-by: Karl Klose <karlklose@google.com>
Commit-Queue: Karl Klose <karlklose@google.com>
2 files changed