Upgrade bazlets to latest stable-2.16 to build with 2.16.20 API

Change-Id: Ia9bf3907b56d99f8aee93ad752aed75f751071dc

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 8c095d4..079e80c 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "22b242638bd36017790d94ffcc18a57f223bda2f",
+    commit = "c40247e30381ddc4a90ef99d749a9161ac4d064b",
     #local_path = "/home/<user>/projects/bazlets",
 )