auth.php: fix some spelling issues in french translation
auth.php: fix some spelling issues in french translation

Abijeet/BookStack,oomba/the-loud-cartographer,oomba/the-loud-cartographer,BookStackApp/BookStack,BookStackApp/BookStack,BookStackApp/BookStack,Abijeet/BookStack,Abijeet/BookStack,oomba/the-loud-cartographer