Add prod.shadow bucket.

Bug: https://github.com/flutter/flutter/issues/141126
Change-Id: I1dee4df777a2baabe7e9a299cea0b71ac1224a13
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/53820
Reviewed-by: Yusuf Mohsinally <mohsinally@google.com>
Reviewed-by: Keyong Han <keyonghan@google.com>
Commit-Queue: Ricardo Amador <ricardoamador@google.com>
diff --git a/recipe_modules/archives/api.py b/recipe_modules/archives/api.py
index 3ca5847..858677d 100644
--- a/recipe_modules/archives/api.py
+++ b/recipe_modules/archives/api.py
@@ -44,7 +44,8 @@
     'prod': 'flutter_infra_release',
     'staging': 'flutter_archives_v2/flutter_infra_release',
     'try': 'flutter_archives_v2/flutter_infra_release',
-    'try.shadow': 'flutter_archives_v2/flutter_infra_release'
+    'try.shadow': 'flutter_archives_v2/flutter_infra_release',
+    'prod.shadow': 'flutter_archives_v2/flutter_infra_release'
 }
 
 # Bucket + initial prefix for artifact destination.