Upgrade bazlets to latest stable-2.16

To use the now mandatory https protocol for MAVEN_CENTRAL.

Bug: Issue 12170
Change-Id: I0e76bc33326b2f9acde6e813c0fc2962dc7be822

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index a7ec139..63cc12f 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "59529f046a5cb855d9fe3ee87110d53305ec69b9",
+    commit = "620a4eb3bc0749301043fd6a69570b61b86e742e",
     #local_path = "/home/<user>/projects/bazlets",
 )