Revert "Move mojo edk into mojo/edk"

mojo/go/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/go/rules.gni")
 
 group("go") {
   deps = [
     ":system_test",
   ]
 }
 
 go_test_binary("system_test") {
   sources = [
     "tests/system_test.go",
   ]
   static_library_sources = [
     "c_embedder/c_embedder.cc",
     "c_embedder/c_embedder.h",
   ]
   deps = [
-    "//mojo/edk/system",
+    "//mojo/system",
   ]
 }