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

Change-Id: Ia4ed4ade76c8b92ad7052ca984936f18cce0c7b6

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index fd2a0c0..714fe3b 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",
 )