gn: Remove obsolete comment about gyp command.

BUG=None
TEST=None
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/296153002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271968 0039d316-1c4b-4281-b951-d872f2087c98

tools/gn/command_gen.cc

@@ -89,7 +89,6 @@ const char kGen_Help[] =
     "\n"
     "  See \"gn help\" for the common command-line switches.\n";
 
-// Note: partially duplicated in command_gyp.cc.
 int RunGen(const std::vector<std::string>& args) {
   base::ElapsedTimer timer;