[cloud functions] Use Firestore transaction api correctly

Change-Id: Icd5ad4cd391fea20017e1b0a01a6d89ead44d43a
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/130800
Reviewed-by: Alexander Thomas <athom@google.com>
diff --git a/functions/node/firestore_impl.dart b/functions/node/firestore_impl.dart
index 8fed82a..4ce1032 100644
--- a/functions/node/firestore_impl.dart
+++ b/functions/node/firestore_impl.dart
@@ -169,7 +169,7 @@
             update.setFieldValue('active_configurations',
                 Firestore.fieldValues.arrayUnion([configuration]));
           }
-          reference.updateData(update);
+          transaction.update(reference, update);
           return approved;
         });
 
diff --git a/results_feed/pubspec.lock b/results_feed/pubspec.lock
index 092dadf..9338777 100644
--- a/results_feed/pubspec.lock
+++ b/results_feed/pubspec.lock
@@ -695,4 +695,4 @@
     source: hosted
     version: "2.2.0"
 sdks:
-  dart: ">=2.6.0 <2.8.0"
+  dart: ">=2.6.0 <=2.8.0-dev.0.0"