Hide headers after storing gnus link

To get the message id when storing links to Gnus articles we toggle all headers on.
This hides the headers again after retrieving the message id.

lisp/org-gnus.el

@@ -140,6 +140,7 @@ If `org-store-link' was called with a prefix arg the meaning of
       (setq desc (org-email-link-description)
 	    link (org-gnus-article-link group newsgroups message-id x-no-archive))
       (org-add-link-props :link link :description desc)
+      (gnus-summary-toggle-header -1)
       link))))
 
 (defun org-gnus-open (path)