[dart:io] Remove DART_IO_DISABLED

runtime/bin/root_certificates_unsupported.cc

Index: runtime/bin/root_certificates_unsupported.cc
diff --git a/runtime/bin/root_certificates_unsupported.cc b/runtime/bin/root_certificates_unsupported.cc
index 55917bdfd732bf1bf52ba756b9813df98ffe46f9..e644665ee4d046713befe0f7c9ac974f95290e20 100644
--- a/runtime/bin/root_certificates_unsupported.cc
+++ b/runtime/bin/root_certificates_unsupported.cc
@@ -2,7 +2,7 @@
 // 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) && !defined(DART_IO_SECURE_SOCKET_DISABLED)
+#if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
 #if defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID) ||                      \
@@ -19,5 +19,4 @@ unsigned int root_certificates_pem_length = 0;
 
 #endif  // defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID) || ...
 
-#endif  // !defined(DART_IO_DISABLED) &&
-        // !defined(DART_IO_SECURE_SOCKET_DISABLED)
+#endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)