Fixing incorrect warning with stimulus-loader v2

Hi Webpackers!

This release fixes an incorrect warning if you're using @symfony/stimulus-bridge version 2. It also outputs a warning if you're using v1 of that library.

yarn upgrade "@symfony/webpack-encore@^1.0.4"

Changes: v1.0.3..v1.0.4

Documentation: http://symfony.com/doc/current/frontend.html

Happy packing!