Fixing getArticleRoute() calls

There is no need to use catslug in Joomla 3.x because:
1. Core content component doesn't use catslug in article URLs;
2. Process link function - **ContentHelperRoute::getArticleRoute** - requires only catid (integer value).
`/components/com_content/helpers/route.php`
`public static function getArticleRoute($id, $catid = 0, $language = 0)`
Merge pull request #5425 from shur/patch-8

Fixing getArticleRoute() calls