import: elpa: Fix typo.

Reported by Eric Dvorsak <eric@dvorsak.fr> on #guix.

* guix/scripts/import/elpa.scm (%default-options): Remove redundant
  quote which led to an error if --archive option was not specified.

guix/scripts/import/elpa.scm

@@ -34,7 +34,7 @@ (define-module (guix scripts import elpa)
 ;;;
 
 (define %default-options
-  '((repo . 'gnu)))
+  '((repo . gnu)))
 
 (define (show-help)
   (display (_ "Usage: guix import elpa PACKAGE-NAME