Remove unused Heroku config

.env.heroku.php

@@ -1,14 +0,0 @@
-<?php
-
-$dbURL = parse_url(getenv('DATABASE_URL'));
-$dbName = substr($dbURL["path"], 1);
-
-return [
-    'APP_DEBUG'    => getenv('APP_DEBUG') ?: false,
-    'DB_HOST'      => $dbURL['host'],
-    'DB_DATABASE'  => $dbName,
-    'DB_USERNAME'  => $dbURL['user'],
-    'DB_PASSWORD'  => $dbURL['pass'],
-    'DB_DRIVER'    => 'pgsql',
-    'CACHE_DRIVER' => 'apc',
-];