Update Dutch password_hint translation to correspond with validation

[maantje]

At the moment the Dutch translation says Minimaal 5 tekens which means your password should be at least 5 characters long. But a 5 character long password is not allowed by the validator.

I think this was a translation error from the English one where it says Must be over 5 characters. To make the Dutch translation correct the Dutch translation should be changed to Minimaal 6 tekens.

/**
 * Get a validator for an incoming registration request.
 *
 * @param  array $data
 * @return \Illuminate\Contracts\Validation\Validator
 */
protected function validator(array $data)
{
    return Validator::make($data, [
        'name' => 'required|max:255',
        'email' => 'required|email|max:255|unique:users',
        'password' => 'required|min:6',
    ]);
}

[ssddanbrown]

Thanks for spotting this @maantje.
I will merge in now ready for the next patch release.