Upgrade bazlets to latest stable-3.1 to build with 3.1.6 API

Change-Id: I3f3be77b67809dd28499e47b635375689084e56d

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index d5516ad..3db37b5 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "51c1fd2758fcc1b900a80d4ebb037bc373f85d39",
+    commit = "69ae6ee516ec1cc51d0a07fe4419a325eb9063ce",
     #local_path = "/home/<user>/projects/bazlets",
 )