EntriesExport/epub: remove TOC page

This change only remove the rendered page of the TOC at the end of the
book, the TOC remains available to readers.

Fixes #3603

Signed-off-by: Kevin Decherf <kevin@kdecherf.com>

src/Wallabag/CoreBundle/Helper/EntriesExport.php

@@ -200,8 +200,6 @@ class EntriesExport
         $hash = sha1(sprintf('%s:%s', $this->wallabagUrl, implode(',', $entryIds)));
         $book->setIdentifier(sprintf('urn:wallabag:%s', $hash), EPub::IDENTIFIER_URI);
 
-        $book->buildTOC();
-
         return Response::create(
             $book->getBook(),
             200,