Fix link (un)escaping.

Thanks for David Bremner <bremner@debian.org> for reporting this
and proposing this fix.

contrib/lisp/org-notmuch.el

@@ -92,8 +92,7 @@ Should accept a notmuch search string as the sole argument."
 
 Can link to more than one message, if so all matching messages are shown."
   (require 'notmuch)
-  (notmuch-show (org-link-unescape search)))
-
+  (notmuch-show search))