Update recipe engine

Change-Id: I31c50a6c45bc2d72f143771b514ba5365c11678b
diff --git a/infra/config/recipes.cfg b/infra/config/recipes.cfg
index fa9c228..83eeb18 100644
--- a/infra/config/recipes.cfg
+++ b/infra/config/recipes.cfg
@@ -5,5 +5,5 @@
   project_id: "recipe_engine"
   url: "https://chromium.googlesource.com/external/github.com/luci/recipes-py.git"
   branch: "master"
-  revision: "b79776cf2fbb4822372bbc03ee9a44318c23af8c"
+  revision: "bb6caf8060139fd4bcefee43f54ae00150e7ce3a"
 }