Upgrade bazlets to latest master to build with 3.1.0-rc2 API

Change-Id: Ia7d30580109f7e09d9ad2233a2c4932ee07bea04

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 61015fd..edb3e74 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "97e83629a68dedda29125657a0a0a8cb21094de1",
+    commit = "cf5be217dc024c5e1a001ff24441bef7ac2d90d0",
     #local_path = "/home/<user>/projects/bazlets",
 )