Translate Action Label

### Description
Simply enable the ability to translate 'Action' label.

### Manual testing scenarios
It is not necessary.

### Contribution checklist
 - [x] Pull request has a meaningful description of its purpose.
 - [X] All commits are accompanied by meaningful commit messages.
 - [X] All automated tests passed successfully (all builds on Travis CI are green).

Author: net32

app/code/Magento/Config/view/adminhtml/templates/system/config/form/field/array.phtml

@@ -21,7 +21,7 @@ $_colspan = $block->isAddAfter() ? 2 : 1;
                 <?php foreach ($block->getColumns() as $columnName => $column): ?>
                     <th><?= /* @escapeNotVerified */ $column['label'] ?></th>
                 <?php endforeach;?>
-                <th class="col-actions" colspan="<?= /* @escapeNotVerified */ $_colspan ?>">Action</th>
+                <th class="col-actions" colspan="<?= /* @escapeNotVerified */ $_colspan ?>"><?= /* @escapeNotVerified */ __('Action') ?></th>
             </tr>
             </thead>
             <tfoot>