Issue #2962594 by quietone: Make source file labels consistent on Credential Form

core/modules/migrate_drupal_ui/src/Form/CredentialForm.php

@@ -188,7 +188,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
 
     $form['source']['source_private_file_path'] = [
       '#type' => 'textfield',
-      '#title' => $this->t('Private file directory'),
+      '#title' => $this->t('Private files directory'),
       '#default_value' => '',
       '#description' => $this->t('To import private files from your current Drupal site, enter a local file directory containing your site (e.g. /var/www/docroot).'),
       '#states' => [

core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php

@@ -94,7 +94,7 @@ public function testMigrateUpgradeExecute() {
     }
     else {
       $session->responseContains('Unable to read from Public files directory.');
-      $session->responseContains('Unable to read from Private file directory.');
+      $session->responseContains('Unable to read from Private files directory.');
     }
 
     // Restart the upgrade process.