Fix mix.exs metadata

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
4 jobs for master in 2 minutes and 46 seconds (queued for 1 second)
Status Name Job ID Coverage
  Check
passed check #583830

00:00:50

 
  Test
passed mix #583831

00:01:06

 
  Deploy
passed pages #583832

00:00:49

failed pages:deploy

00:00:00