Fix message format in org-notmuch-search-open

* org-notmuch.el (org-notmuch-search-open): Bug fix
When opening a notmuch-search link, we use =message= to display the
path at the bottom of the screen.  This would signal "Not enough
arguments for format string" when the path contained %-signs, as it is
likely to when the query contains spaces:
[[notmuch-search:tag:inbox%2520not%2520tag:bulk%2520org]]

That query appears to be double-escaped, which also might contribute
to the problem, but either way: we should use =(message "%s" str)= to
print arbitrary strings, not =(message str)=.

contrib/lisp/org-notmuch.el

@@ -113,7 +113,7 @@ Can link to more than one message, if so all matching messages are shown."
 
 (defun org-notmuch-search-open (path)
   "Follow a notmuch message link specified by PATH."
-  (message path)
+  (message "%s" path)
   (funcall org-notmuch-search-open-function path))
 
 (defun org-notmuch-search-follow-link (search)