make:registration-form form class has invalid phpcs

[weaverryan]

The new make:registration-form generates a little bit of invalid PHPcs in the form class. It's not caught (for some reason) by our phpcs-fixer, which we run on the classes (not sure why). We should fix that and the bad phpcs.

See the last line for the bad phpcs:

        $builder
            ->add('email')
            ->add('plainPassword', PasswordType::class, [
                // instead of being set onto the object directly,
                // this is read and encoded in the controller
                'mapped' => false,
                'constraints' => [
                    new NotBlank([
                        'message' => 'Please enter a password',
                    ]),
                    new Length([
                        'min' => 6,
                        'minMessage' => 'Your password should be at least {{ limit }} characters',
                    ]),
                ],            ])
        ;