dart2js: Don't show "--enable-concrete-type-inference" in help.

pkg/compiler/lib/src/dart2js.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.cmdline;
 
 import 'dart:async'
     show Future, EventSink;
 import 'dart:convert' show UTF8, LineSplitter;
 import 'dart:io'
@@ skipping 570 matching lines @@
   --throw-on-error
     Throw an exception if a compile-time error is detected.
 
   --library-root=<directory>
     Where to find the Dart platform libraries.
 
   --allow-mock-compilation
     Do not generate a call to main if either of the following
     libraries are used: dart:dom, dart:html dart:io.
 
-  --enable-concrete-type-inference
-    Enable experimental concrete type inference.
-
   --disable-native-live-type-analysis
     Disable the optimization that removes unused native types from dart:html
     and related libraries.
 
   --categories=<categories>
     A comma separated list of allowed library categories.  The default
     is "Client".  Possible categories can be seen by providing an
     unsupported category, for example, --categories=help.  To enable
     all categories, use --categories=all.
 
@@ skipping 116 matching lines @@
       } else if (exitCode == 253) {
         print(">>> TEST CRASH");
       } else {
         print(">>> TEST FAIL");
       }
       stderr.writeln(">>> EOF STDERR");
       subscription.resume();
     });
   });
 }