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

Change-Id: I0a7b1b21f4b9eca5e9a2684b8f186abc0894d28e

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 813afc0..41c4eaf 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",
 )