Updated logic to generate random short codes, increasing entropy

config/autoload/url-shortener.global.php

@@ -2,8 +2,6 @@
 
 declare(strict_types=1);
 
-use Shlinkio\Shlink\Core\Options\UrlShortenerOptions;
-
 use function Shlinkio\Shlink\Common\env;
 
 return [
@@ -13,7 +11,6 @@ return [
             'schema' => env('SHORTENED_URL_SCHEMA', 'http'),
             'hostname' => env('SHORTENED_URL_HOSTNAME'),
         ],
-        'shortcode_chars' => env('SHORTCODE_CHARS', UrlShortenerOptions::DEFAULT_CHARS),
         'validate_url' => true,
         'not_found_short_url' => [
             'enable_redirection' => false,