Remoting_nacl build shouldn't need to depend on nacl_irt.

Allow building in parallel. It may be a runtime dependency
but it's not a build-time dependency.

Happened to notice the serialization in the graph:
http://chromium-build-stats.appspot.com/ninja_log/2015/02/05/build48-m1/ninja_log.build48-m1.chrome-bot.20150205-093049.13303.gz/trace.html

BUG=none

Review URL: https://codereview.chromium.org/902033002

Cr-Commit-Position: refs/heads/master@{#314941}

remoting/remoting_nacl.gyp

@@ -182,7 +182,6 @@
         '../native_client/tools.gyp:prep_toolchain',
         '../native_client_sdk/native_client_sdk_untrusted.gyp:nacl_io_untrusted',
         '../net/net_nacl.gyp:net_nacl',
-        '../ppapi/native_client/native_client.gyp:nacl_irt',
         '../ppapi/native_client/native_client.gyp:ppapi_lib',
         '../ppapi/ppapi_nacl.gyp:ppapi_cpp_lib',
         '../third_party/expat/expat_nacl.gyp:expat_nacl',