[12.x] Add APP_NAME fallback in mail config (#6755)

The `MAIL_FROM_NAME` config value falls back to the generic "Example"
when unset. This updates the fallback to use `APP_NAME` instead,
matching the convention in `.env.example` where `MAIL_FROM_NAME`
references `${APP_NAME}`.

config/mail.php

@@ -112,7 +112,7 @@ return [
 
     'from' => [
         'address' => env('MAIL_FROM_ADDRESS', 'hello@example.com'),
-        'name' => env('MAIL_FROM_NAME', 'Example'),
+        'name' => env('MAIL_FROM_NAME', env('APP_NAME', 'Laravel')),
     ],
 
 ];