gnu: ebook: Drop circular inclusion of the module into itself.

* gnu/packages/ebook.scm: Do not import (gnu packages ebook).

gnu/packages/ebook.scm

@@ -25,7 +25,6 @@ (define-module (gnu packages ebook)
   #:use-module (guix build-system python)
   #:use-module (gnu packages)
   #:use-module (gnu packages databases)
-  #:use-module (gnu packages ebook)
   #:use-module (gnu packages fontutils)
   #:use-module (gnu packages freedesktop)
   #:use-module (gnu packages glib)