Pictograms are not well rendered on theme change

[annelhote]

Describe the bug
On the home page, pictograms are not correctly displayed in dark mode, but on Firefox and co (librewolf) ! But not on chrome or Brave.

To Reproduce

• Open the web site : https://scanr.enseignementsup-recherche.gouv.fr/
• On the header, click on "Paramètres d'affichage" and choose "Thème sombre"
  => Pictograms render not well

On Firefox, the render is :