Upgrade bazlets to latest stable-2.15 to build with 2.15.11 API

Change-Id: Ic11d38798ee717e29bf4ab934388d0c4be13f0ab

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 2a52e6e..fea24d6 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "2b1d68959119920e5fa9bdfb9f0cf926bfef4929",
+    commit = "90314da56cc057c2c8201dab43dfa98e84235957",
     #local_path = "/home/<user>/projects/bazlets",
 )