Clean up Views join plugins

1. +++ b/core/modules/views/lib/Drupal/views/Plugin/views/join/JoinPluginBase.php
   @@ -46,8 +46,6 @@
   - * @todo It might make sense to create an interface for joins.
   - *
     * Extensions of this class can be used to create more interesting joins.
   

   Note for other people: we decided that view is not in the state of support it.

2. +++ b/core/modules/views/lib/Drupal/views/Plugin/views/join/Subquery.php
   @@ -2,19 +2,18 @@
   + *   same as Drupal\views\Plugin\views\join\JoinPluginBase, except:
   

   Should this have a starting "\"?

3. +++ b/core/modules/views/lib/Drupal/views/Plugin/views/join/Subquery.php
   @@ -31,16 +30,14 @@ public function __construct(array $configuration, $plugin_id, array $plugin_defi
   +   * @param @param \Drupal\views\Plugin\views\query\QueryPluginBase $view_query
   

   @param @param @param @paaaaaaaram

Thank you!

The only thing i'm not sure of is the capital "E.g" but that's easy enough to clean up after.

Committed and pushed to 8.x. Thanks!