Make failure notification parameter a list

Change-Id: I7a1721f648b27ef9e149a219ab1bc5aaac28a818
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/19900
Reviewed-by: Jason Simmons <jsimmons@google.com>
Reviewed-by: Dan Field <dnfield@google.com>
Commit-Queue: Dan Field <dnfield@google.com>
diff --git a/recipes/infra/ci_yaml.py b/recipes/infra/ci_yaml.py
index ccf9105..d402c92 100644
--- a/recipes/infra/ci_yaml.py
+++ b/recipes/infra/ci_yaml.py
@@ -110,7 +110,7 @@
             gerrit_project = 'infra',
             repo_dir = infra_path,
             commit_message = 'Roll %s to %s' % (repo, git_ref),
-            cc_on_failure = 'flutter-infra@grotations.appspotmail.com',
+            cc_on_failure = ['flutter-infra@grotations.appspotmail.com'],
             labels_to_set = {'Code-Review': 2},
         )