Upgrade bazlets to latest stable-2.15 to build with 2.15.14 API

Change-Id: I6956a26456549414c5c065832aeebee2dae24c85

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index ca671f9..1e0171d 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "70d6ae0cee03c456fa4b32c807f3d13c032ef498",
+    commit = "a2830809bc277f55e094e8203fee04d9dc802e51",
     #local_path = "/home/<user>/projects/bazlets",
 )