Change Pager.php for support pgsql

In pgsql, the pager launchs this Exception ...

An exception has been thrown during the rendering of a template ("An exception occurred while executing 'SELECT count(DISTINCT n0_.id) AS sclr0 FROM news__post n0_ LEFT JOIN news__post_tag n2_ ON n0_.id = n2_.post_id LEFT JOIN classification__tag c1_ ON c1_.id = n2_.tag_id AND (c1_.enabled = true) LEFT JOIN fos_user_user f3_ ON n0_.author_id = f3_.id AND (f3_.enabled = true) WHERE n0_.enabled = ? ORDER BY n0_.publication_date_start DESC' with params ["true"]:

Resetting dql OrderBy fix the bug