Upgrade bazlets to latest stable-2.16 to build with 2.16.21 API

Change-Id: I8db745a43cf5f4e9b50e6072c73e06fb80e15e64

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 079e80c..908791b 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "c40247e30381ddc4a90ef99d749a9161ac4d064b",
+    commit = "fff6f20bb2eceaf872a8acf8ad51471c25a82d38",
     #local_path = "/home/<user>/projects/bazlets",
 )