Remove APP_DEBUG from compose.override.dist.yml (#1067)

This env variable can be set via `.env` and `.env.*`, and is already
being set that way. Specifying it here not only makes it redundant, but
also disables the logic of this value being dynamically assigned
depending on `APP_ENV`

compose.override.dist.yml

@@ -7,7 +7,6 @@ services:
                 condition: service_healthy
         environment:
             # You can move these environment variables to your .env.local file
-            APP_DEBUG: 0
             APP_ENV: ${ENV:-prod}
             APP_SECRET: EDITME
             DATABASE_URL: "mysql://root@mysql/sylius_%kernel.environment%"