Steps to reproduce

1. Create two locales one = Locale('en') and two = Locale('en', '')
2. Log both

This is an exact duplicate of #43607. That issue was fixed for native platforms but not for web platforms. The same fix should be applied to https://github.com/flutter/flutter/blob/master/engine/src/flutter/lib/web_ui/lib/platform_dispatcher.dart and https://github.com/flutter/flutter/blob/master/engine/src/flutter/lib/web_ui/lib/src/engine/platform_dispatcher.dart

Expected results

Both should print as en.

Actual results

See that one is en and two is en_

Code sample

import 'package:flutter/material.dart';

void main() {
  print(Locale('en'));
  print(Locale('en', ''));
}

Screenshots or Video

N/A

Logs

N/A

Flutter Doctor output

N/A