Use https when linking to symfony.com

Author: javiereguiluz

symfony/flex/1.0/.env.dist

@@ -1,3 +1,3 @@
 # This file is a "template" of which env vars needs to be defined in your configuration or in an .env file
 # Set variables here that may be different on each deployment target of the app, e.g. development, staging, production.
-# http://symfony.com/doc/current/best_practices/configuration.html#infrastructure-related-configuration
+# https://symfony.com/doc/current/best_practices/configuration.html#infrastructure-related-configuration