[cloud functions] Remove from the correct configurations array

Active results should only be removed from the active_results array.
Removing them from the configurations caused yesterday's result feed
outage and may have contributed to the multiple active result problems as
well.

Fixes https://github.com/dart-lang/dart_ci/issues/73

TBR=sortie

Change-Id: Ic3d875fcb75155a81809a411dd2031f57dd17867
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/134301
Reviewed-by: Alexander Thomas <athom@google.com>
diff --git a/functions/node/firestore_impl.dart b/functions/node/firestore_impl.dart
index d4bbf32..6bbf2b1 100644
--- a/functions/node/firestore_impl.dart
+++ b/functions/node/firestore_impl.dart
@@ -242,8 +242,8 @@
       Map<String, dynamic> activeResult, String configuration) async {
     final updateData = UpdateData();
     if (activeResult['configurations'].length > 1) {
-      updateData.setFieldValue(
-          'configurations', Firestore.fieldValues.arrayRemove([configuration]));
+      updateData.setFieldValue('active_configurations',
+          Firestore.fieldValues.arrayRemove([configuration]));
     } else {
       updateData.setFieldValue(
           'active_configurations', Firestore.fieldValues.delete());