use no flag at all instead of explicit --dev in composer calls
use no flag at all instead of explicit --dev in composer calls

prevents deprecation warning from Composer

a2service/heroku-buildpack-php,dzuelke/heroku-buildpack-php,jayelkaake/heroku-buildpack-magento,puteulanus/heroku-buildpack-php,emeth-/heroku-buildpack-php,puteulanus/heroku-buildpack-php,alzheic/heroku-buildpack-aop,alzheic/heroku-buildpack-aop,heroku/heroku-buildpack-php,emeth-/heroku-buildpack-php,heroku/heroku-buildpack-php,puteulanus/heroku-buildpack-php,heroku/heroku-buildpack-php,thecsea/heroku-buildpack-php-with-ioncube,thecsea/heroku-buildpack-php-with-ioncube,a2service/heroku-buildpack-php,jayelkaake/heroku-buildpack-magento,jayelkaake/heroku-buildpack-magento,thecsea/heroku-buildpack-php-with-ioncube,a2service/heroku-buildpack-php,alzheic/heroku-buildpack-aop,heroku/heroku-buildpack-php,dzuelke/heroku-buildpack-php,emeth-/heroku-buildpack-php,dzuelke/heroku-buildpack-php,emeth-/heroku-buildpack-php