OWNERS: Add roller for recipes.py

Sometimes trivial rolls modify recipes.py in addition to
infra/config/recipes.cfg. Example: http://go/flutter-cl/recipes/+/32161.

Change-Id: I80b65ad7eccd1f2fe64bfd852523c1062b8b2208
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/32141
Reviewed-by: Casey Hillers <chillers@google.com>
Commit-Queue: Rob Mohr <mohrr@google.com>
Commit-Queue: Casey Hillers <chillers@google.com>
diff --git a/OWNERS b/OWNERS
index 40721bb..2767d39 100644
--- a/OWNERS
+++ b/OWNERS
@@ -9,3 +9,4 @@
 zra@google.com
 
 per-file infra/config/recipes.cfg=flutter-prod-builder@chops-service-accounts.iam.gserviceaccount.com
+per-file recipes.py=flutter-prod-builder@chops-service-accounts.iam.gserviceaccount.com