Update top level SUBMITTING_PATCHES

This document is out of date, the URLs are from last August.
Direct readers to the new server.

Change-Id: Ib4a66a397c96109bc375d5142c97aa9ef9dc4f7c
diff --git a/Documentation/dev-readme.txt b/Documentation/dev-readme.txt
index 2490695..552b5a8 100644
--- a/Documentation/dev-readme.txt
+++ b/Documentation/dev-readme.txt
@@ -11,7 +11,7 @@
 Create a new client workspace:
 
 ----
-  git clone https://code.google.com/p/gerrit
+  git clone https://gerrit.googlesource.com/gerrit
   cd gerrit
 ----