Upgrade bazlets to latest stable-2.16 to build with 2.16.4 API

Change-Id: Ic2eb4ffdda92a1dc0a86ac3420c8cb027f456b3d

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 6a69034..608cb95 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "09a18a88ebdada986d32c1f50581e8734a47939a",
+    commit = "c15e64db2a87c0453427ff45f79d1ed3899b5d92",
     #local_path = "/home/<user>/projects/bazlets",
 )