Fix backtick in org-odt-inline-image-rules

* lisp/ox-odt.el (org-odt-inline-image-rules): Fix error to make the
  list evaluate inline code at definition.

lisp/ox-odt.el

@@ -743,7 +743,7 @@ link's path."
 		:value-type (regexp :tag "Path")))
 
 (defcustom org-odt-inline-image-rules
-  '(("file" . ,(regexp-opt '(".jpeg" ".jpg" ".png" ".gif" ".svg")))
+  `(("file" . ,(regexp-opt '(".jpeg" ".jpg" ".png" ".gif" ".svg")))
     ("attachment" . ,(regexp-opt '(".jpeg" ".jpg" ".png" ".gif" ".svg"))))
   "Rules characterizing image files that can be inlined into ODT.