Don't trim current_password (laravel#5546)

Inspired by laravel/framework#36415

As JetStream/Fortify uses a `current_password` field when allowing a user to change their password, and as JetStream is one of the starter kits listed on the docs, this PR adds `current_password` in the `$except` option of the `TrimStrings` middleware.

Author: rodrigopedra

app/Http/Middleware/TrimStrings.php

@@ -12,6 +12,7 @@ class TrimStrings extends Middleware
      * @var array
      */
     protected $except = [
+        'current_password',
         'password',
         'password_confirmation',
     ];