Adds missing use statement for Locale

Fixes an error when translating the description if the propagation method is set to PROPAGATION_METHOD_LANGUAGE

src/fields/SuperTableField.php

@@ -30,6 +30,7 @@
 use craft\helpers\Gql as GqlHelper;
 use craft\helpers\Json;
 use craft\helpers\StringHelper;
+use craft\i18n\Locale;
 use craft\queue\jobs\ApplyNewPropagationMethod;
 use craft\queue\jobs\ResaveElements;
 use craft\services\Elements;