Revert "gnu: calibre: Update to 2.30.0."

The new version requires the SSL package from Python >= 2.7.9.

This reverts commit d571101770.

gnu/packages/ebook.scm

@@ -60,7 +60,7 @@
 (define-public calibre
   (package
     (name "calibre")
-    (version "2.30.0")
+    (version "2.29.0")
     (source
       (origin
         (method url-fetch)
@@ -69,7 +69,7 @@
                             version ".tar.xz"))
         (sha256
           (base32
-           "1k2rpn06nfzqjy5k6fh8pwfj8vbhpn7rgkpkkpz5n2fqg3z8ph1j"))
+           "1n3cfnjnghhhsgzcbcvbr0gh191lhl6az09q1s68jhlcc2lski6l"))
         ;; Remove non-free or doubtful code, see
         ;; https://lists.gnu.org/archive/html/guix-devel/2015-02/msg00478.html
         (modules '((guix build utils)))