That's because the old street sign was not removed.

Here's a more official source:

https://www.facebook.com/maarifcom/posts/pfbid02p4uzCoXE4DYvTwQhMtXxebBscLoDqaijdKZ26onpzuT6PDzBrASvbhXrq5Jq3opRl

It's from the official page of the district where the street is. Translation:

Honoring the nation’s great figures… As part of an initiative by the Al Maarif District Council, and with the approval of the Casablanca City Council, the park located in the Al Batha neighborhood has been named after the artist and minister Thouria Jebrane, the street formerly known as Mammar Loud has been named after Minister Mohamed El Ouafa, and Dr. Mahdi Elmandjra’s name has been given to Rue des Papillons."