Upgrade bazlets to latest stable-2.16 to build with 2.16.16 API

Change-Id: I6f4388b98d34addce49ca6ef7da40808e1fbf450

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 015f04e..60de8a2 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "577450c73780560972f8a1a92c91410192ff7224",
+    commit = "1b6fc9b39001806b37a4eedbb0a4816daf1a227d",
     #local_path = "/home/<user>/projects/bazlets",
 )