[BUG] [Button] Variant primary doesn't work with dark mode

[kevin-carangeot]

Context

The variant "Primary" doesn't work if the navigator is in dark mode.

Reproduce link

https://uikit.prestashop.com/?path=/docs/components-button--docs

Steps to Reproduce

Activate dark mode on Google Chrome

1. Parameters
2. Apparence
3. Theme
4. Sombre

Expected Behavior

Variant Primary:

Current Behavior

Variant Primary:

Additional comments

This CSS is added