Revert "[ruby/webrick] Add test for shutdown_pipe"

This reverts commit c06eab1329.

test/webrick/test_server.rb

@@ -161,18 +161,6 @@ class TestWEBrickServer < Test::Unit::TestCase
     }
   end
 
-  def test_shutdown_pipe
-    pipe = IO.pipe
-    server = WEBrick::GenericServer.new(
-      :ShutdownPipe => pipe,
-      :BindAddress => '0.0.0.0',
-      :Port => 0,
-      :Logger => WEBrick::Log.new([], WEBrick::BasicLog::WARN))
-    server_thread = Thread.start { server.start }
-    pipe.last.puts('')
-    assert_join_threads([server_thread])
-  end
-
   def test_port_numbers
     config = {
       :BindAddress => '0.0.0.0',