Upgrade bazlets to latest master revision

Includes the following fixes relevant to this project:

bec81c8 - Bazel: Add remaining fixes for --incompatible_disallow_legacy_java_provider

Change-Id: I8ab958d7d8a7655be9274e09a66c8fe84b2efe23

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 11dcf72..863fce2 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -21,7 +21,7 @@
 load("//tools:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "09a035e98077dce549d5f6a7472d06c4b8f792d2",
+    commit = "bf900bbe58f7a7802799d6d6477567b05ab2f399",
     # local_path = "/home/<user>/projects/bazlets",
 )