User Password Without Confirm

To remove the user password confirm field, change the field type from password_confirm to password.

function mantraprofile_form_alter(&$form, $form_state, $form_id) {
  if ($form_id == 'user_register_form') {
    if (!empty($form['account']['pass'])) {
      $form['account']['pass']['#type'] = 'password';
      $form['account']['pass']['#title'] = t('Password');
    }
  }
}