Loading do_feed_rss2 function with do_action

[vitrix]

Describe the bug
The job feed https://www.example.com/?feed=job_feed created by this plug uses the default Wordpress do_feed_rss2.
We want to add a additional action to the do_feed_rss2 action, but this is not possible, because in wp-job-manager/includes/class-wp-job-manager-post-types.php the function do_feed_rss2(false) is called directly.

To Reproduce
Steps to reproduce the behavior:

1. Add a do_action behavior to do_feed_rss2
2. Call the /?feed=job_feed page and you will notice your custom action is not activated.

Expected behavior
In "wp-job-manager/includes/class-wp-job-manager-post-types.php the do_feed_rss2(false) should be replaced with do_action('do_feed_rss2');.
This way customers can add extra actions to the feed.

[masteradhoc]

@vitrix could you check please the implementation in #2892 if that works for you? then let's hope it gets implemented soon :)

[vitrix]

@masteradhoc can confirm with this change it still works for me