Remove unnecessary async

packages/path_provider/path_provider_linux/example/lib/main.dart

@@ -4,7 +4,7 @@ import 'dart:async';
 import 'package:flutter/services.dart';
 import 'package:path_provider_linux/path_provider_linux.dart';
 
-void main() async {
+void main() {
   runApp(MyApp());
 }
 

packages/path_provider/path_provider_macos/example/lib/main.dart

@@ -9,7 +9,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
 
-void main() async {
+void main() {
   runApp(MyApp());
 }
 

packages/path_provider/path_provider_windows/example/lib/main.dart

@@ -9,7 +9,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:path_provider_windows/path_provider_windows.dart';
 
-void main() async {
+void main() {
   runApp(MyApp());
 }