bug #377 Fix Deploying to the Heroku (bocharsky-bw)

This PR was squashed before being merged into the master branch (closes #377).

Discussion
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Fix Deploying to the Heroku

Fix #371 .

Let's use SQLite DB with pre-populated data instead of bootstrapping a new PostgreSQL one:

It works for me: https://symfony-demo.herokuapp.com

Commits
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662e78f Fix Deploying to the Heroku

Author: javiereguiluz

app.json

@@ -9,18 +9,12 @@
     "repository": "https://github.com/symfony/symfony-demo",
     "logo": "https://symfony.com/images/v5/pictos/demoapp.svg?v=4",
     "success_url": "/",
-    "scripts": {
-        "postdeploy": "php bin/console doctrine:schema:create && php bin/console doctrine:fixtures:load -n"
-    },
     "env": {
         "SYMFONY_ENV": "prod",
         "SYMFONY_SECRET": {
             "description": "Extra entropy for %kernel.secret%; used for CSRF tokens, cookies and signed URLs.",
             "generator": "secret"
         }
     },
-    "addons": [
-        "heroku-postgresql"
-    ],
     "image": "heroku/php"
 }