[dart:io] Remove DART_IO_DISABLED

runtime/bin/eventhandler_fuchsia.cc

Index: runtime/bin/eventhandler_fuchsia.cc
diff --git a/runtime/bin/eventhandler_fuchsia.cc b/runtime/bin/eventhandler_fuchsia.cc
index 41aa9cc908c3d71301e96edf61e4603190e1bbf0..cd103b7f0cf7040a07ac1ad4d6c0970fb2aab18a 100644
--- a/runtime/bin/eventhandler_fuchsia.cc
+++ b/runtime/bin/eventhandler_fuchsia.cc
@@ -2,8 +2,6 @@
 // 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.
 
-#if !defined(DART_IO_DISABLED)
-
 #include "platform/globals.h"
 #if defined(HOST_OS_FUCHSIA)
 
@@ -560,5 +558,3 @@ uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
 }  // namespace dart
 
 #endif  // defined(HOST_OS_FUCHSIA)
-
-#endif  // !defined(DART_IO_DISABLED)