[Site] Fix input range color

Previous value made it impossible to use without a background.

Author: smnandre

ux.symfony.com/assets/styles/_variables.scss

@@ -19,5 +19,5 @@ $size-unit: calc(8px + 1.5625vw);
 
 $font-family-monospace: var(--font-family-code);
 
-$form-range-track-bg: var(--bs-body-bg);
+$form-range-track-bg: #111315ab;
 $form-range-thumb-bg: var(--bs-secondary-color);