build: update to latest lighting-onion commit

This commit updates `lnd` to the latest version of our Sphinx repo as
it has included a bug fix to use the proper version within the Sphinx
routing header.

glide.yaml

@@ -56,7 +56,7 @@ import:
 - package: google.golang.org/grpc
   version: b3ddf786825de56a4178401b7e174ee332173b66
 - package: github.com/lightningnetwork/lightning-onion
-  version: 7625644d9f0584d63d4da902e51b1d7d921022bf
+  version: 1d52214c016402c9cb78d479895afb370597b488
 - package: github.com/grpc-ecosystem/grpc-gateway
   version: f2862b476edcef83412c7af8687c9cd8e4097c0f
 - package: github.com/go-errors/errors