Fold //ipc/mojo into //ipc.

tools/ipc_fuzzer/message_replay/BUILD.gn

 # Copyright 2016 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.
 
 executable("ipc_fuzzer_replay") {
   configs += [ "//tools/ipc_fuzzer:ipc_fuzzer_tool_config" ]
   deps = [
-    "//ipc/mojo",
+    "//ipc",
     "//mojo/edk/system",
     "//tools/ipc_fuzzer/message_lib:ipc_message_lib",
   ]
   sources = [
     "replay.cc",
     "replay_process.cc",
     "replay_process.h",
   ]
 }