Backport commit c1cacb0 from Emacs master branch

* lisp/org-gnus.el (org-gnus-no-new-news):
Prefer (substitute-command-keys "`\\[foo-command]'")
to "`M-x foo-command'" in docstrings and the like.

Avoid hard-coding "M-x command" in docstrings
c1cacb09948928287bfc32745f2a92604d3291c4
Paul Eggert
Fri Aug 21 14:09:47 2015 -0700

lisp/org-gnus.el

@@ -295,7 +295,7 @@ If `org-store-link' was called with a prefix arg the meaning of
 	(group (gnus-group-jump-to-group group))))
 
 (defun org-gnus-no-new-news ()
-  "Like `M-x gnus' but doesn't check for new news."
+  "Like `\\[gnus]' but doesn't check for new news."
   (if (not (gnus-alive-p)) (if org-gnus-no-server (gnus-no-server) (gnus))))
 
 (provide 'org-gnus)