Remove mandrill as a default configuration since it's fallen out of popularity.

config/services.php

@@ -8,7 +8,7 @@ return [
     |--------------------------------------------------------------------------
     |
     | This file is for storing the credentials for third party services such
-    | as Stripe, Mailgun, Mandrill, and others. This file provides a sane
+    | as Stripe, Mailgun, SparkPost and others. This file provides a sane
     | default location for this type of information, allowing packages
     | to have a conventional place to find your various credentials.
     |
@@ -19,10 +19,6 @@ return [
         'secret' => env('MAILGUN_SECRET'),
     ],
 
-    'mandrill' => [
-        'secret' => env('MANDRILL_SECRET'),
-    ],
-
     'ses' => [
         'key' => env('SES_KEY'),
         'secret' => env('SES_SECRET'),