Query article number from file is nil by default

* org-gnus.el (org-gnus-nnimap-query-article-no-from-file): Query
article number from file is nil by default.

The function function `nnimap-group-overview-filename' is gone in Gnus
devel.  Subsequently enabling this feature by default will cause
org-gnus to fail on Emacs24.

Thanks for Matt Lundin for pointing this out.

lisp/org-gnus.el

@@ -55,7 +55,7 @@ negates this setting for the duration of the command."
   :group 'org-link-store
   :type 'boolean)
 
-(defcustom org-gnus-nnimap-query-article-no-from-file t
+(defcustom org-gnus-nnimap-query-article-no-from-file nil
   "If non-nil, `org-gnus-follow-link' will try to translate
 Message-Ids to article numbers by querying the .overview file.
 Normally, this translation is done by querying the IMAP server,