Fix phpcs issues.

Closes #3458515

src/Annotation/AggregatorFetcher.php

@@ -7,7 +7,7 @@ use Drupal\Component\Annotation\Plugin;
 /**
  * Defines a Plugin annotation object for aggregator fetcher plugins.
  *
- * Plugin Namespace: Plugin\aggregator\fetcher
+ * Plugin Namespace: Plugin\aggregator\fetcher.
  *
  * For a working example, see \Drupal\aggregator\Plugin\aggregator\fetcher\DefaultFetcher
  *