Selecting quality setting duplicates provider selection.

Problem/Motivation

When submitting a new job, the UI is usable, but glitchy. In the "Provider" dropdown menu, when selecting "Gengo translator", the current "Checkout settings" collapsible area is changed to Gengo's, which is fine, but everytime the "Quality" option is changed, a new "Provider" dropdown menu and Gengo logo is appended to the area, which can lead to this kind of UI :

Proposed resolution

The form is constructed in checkoutSettingsForm() of Drupal\tmgmt_mygengo\MyGengoTranslatorUi. The AJAX callback function for the "Quality" dropdown menu looks wrong :

    $settings['quality'] = array(
      '#type' => 'select',
      '#title' => t('Quality'),
      '#options' => $this->getAvailableTiersOptions($job),
      '#default_value' => $job->getSetting('quality'),
      '#description' => t('Choose the level of quality for this translation job.'),
      '#ajax' => array(
        'callback' => '::ajaxTranslatorSelect',
        'wrapper' => 'tmgmt-ui-translator-settings',
      ),
    );

The callback function is defined in Drupal\tmgmt\Form\JobForm.

Remaining tasks

Most likely implement a different callback function, as ajaxTranslatorSelect looks fine.