src: don't set --icu_case_mapping flag on startup

It's on by default now and the flag will be removed in the near future.

Fixes: nodejs/node#13688
PR-URL: nodejs/node#13698
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

src/node.cc

@@ -4228,14 +4228,6 @@ void Init(int* argc,
                             DispatchDebugMessagesAsyncCallback));
   uv_unref(reinterpret_cast<uv_handle_t*>(&dispatch_debug_messages_async));
 
-#if defined(NODE_HAVE_I18N_SUPPORT)
-  // Set the ICU casing flag early
-  // so the user can disable a flag --foo at run-time by passing
-  // --no_foo from the command line.
-  const char icu_case_mapping[] = "--icu_case_mapping";
-  V8::SetFlagsFromString(icu_case_mapping, sizeof(icu_case_mapping) - 1);
-#endif
-
 #if defined(NODE_V8_OPTIONS)
   // Should come before the call to V8::SetFlagsFromCommandLine()
   // so the user can disable a flag --foo at run-time by passing