[flutter_runner] remove args from generated main

A regression in the flutter_runner prevents flutter
main methods to have an args parameter. Since, we
are not using the args we remove it here.

TEST=None

Change-Id: I212c8577005d87c237bc1c1cb6c0a0219f252ea0
diff --git a/runtime/flutter_runner/build/gen_debug_wrapper_main.py b/runtime/flutter_runner/build/gen_debug_wrapper_main.py
index 00f4e24..a3d3500 100755
--- a/runtime/flutter_runner/build/gen_debug_wrapper_main.py
+++ b/runtime/flutter_runner/build/gen_debug_wrapper_main.py
@@ -38,7 +38,7 @@
 ''')
   outfile.write("import '%s' as flutter_app_main;\n" % args.main_dart)
   outfile.write('''
-void main(List<String> args) async {
+void main() async {
   assert(await (() async {
     // TODO(awdavies): Use the logger instead.
     print('Overriding app main method because flutter_driver_extendable '