Fix escaping of spaces when passing launch arguments to the iOS device. (#5574)

`Process.start` seems to be escaping as needed.
diff --git a/packages/flutter_tools/lib/src/ios/devices.dart b/packages/flutter_tools/lib/src/ios/devices.dart
index bf96b72..328f45b 100644
--- a/packages/flutter_tools/lib/src/ios/devices.dart
+++ b/packages/flutter_tools/lib/src/ios/devices.dart
@@ -231,7 +231,7 @@
 
     if (launchArguments.length > 0) {
       launchCommand.add('--args');
-      launchCommand.add('"${launchArguments.join(" ")}"');
+      launchCommand.add('${launchArguments.join(" ")}');
     }
 
     int installationResult = -1;