Unlocalized string in dotnet build --help output.

[peterhuene]

Steps to reproduce

1. DOTNET_CLI_UI_LANGUAGE=es dotnet build --help

Expected behavior

The PROJECT argument description is localized into Spanish.

Actual behavior

The PROJECT argument description is still in English.

...
Argumentos:
  <PROYECTO>   The MSBuild project file to build. If a project file is not specified, MSBuild searches the current working directory for a file that has a file extension that ends in `proj` and uses that file.
...

Environment data

$ dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   2.1.400-preview-008836
 Commit:    309ca68e41

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  10.13
 OS Platform: Darwin
 RID:         osx-x64
 Base Path:   /Users/peterhuene/src/cli/bin/2/osx-x64/dotnet/sdk/2.1.400-preview-008836/

Host (useful for support):
  Version: 2.1.0-rc1-26423-06
  Commit:  b50a96ee38

.NET Core SDKs installed:
  2.1.400-preview-008836 [/Users/peterhuene/src/cli/bin/2/osx-x64/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.0-rc1-30661 [/Users/peterhuene/src/cli/bin/2/osx-x64/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.0-rc1-30661 [/Users/peterhuene/src/cli/bin/2/osx-x64/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.0-rc1-26423-06 [/Users/peterhuene/src/cli/bin/2/osx-x64/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

[peterhuene]

I'm fixing this as part of the help scrub.