Remove useless validation rules from import code

[MAILPOET-2432]

assets/js/src/subscribers/importExport/import/step_data_manipulation/do_import.jsx

@@ -34,11 +34,10 @@ export default (subscribersToImport, segments, updateExistingSubscribers, onImpo
   _.each(jQuery('select.mailpoet_subscribers_column_data_match'),
     (column, columnIndex) => {
       const columnId = jQuery(column).data('column-id');
-      const validationRule = jQuery(column).data('validation-rule');
       if (columnId === 'ignore') {
         return;
       }
-      columns[columnId] = { index: columnIndex, validation_rule: validationRule };
+      columns[columnId] = { index: columnIndex };
     });
 
   _.each(clickSubscribers, () => {

assets/js/src/subscribers/importExport/import/step_data_manipulation/generate_column_selection.jsx

@@ -68,7 +68,6 @@ export default () => {
                   });
               });
             jQuery(selectElement).data('column-id', newColumnData.id);
-            jQuery(selectElement).data('validation-rule', false);
             // close popup
             MailPoet.Modal.close();
           }).fail((response) => {

assets/js/src/subscribers/importExport/import/step_data_manipulation/match_table.jsx

@@ -19,7 +19,6 @@ function ColumnDataMatch({ header, subscribers }) {
             <select
               className="mailpoet_subscribers_column_data_match"
               data-column-id={columnType.column_id}
-              data-validation-rule="false"
               data-column-index={i}
               id={`column_${i}`}
             />