Fix accordion: use $accordion-color rather than computing it via colo…

…r-contrast

scss/_accordion.scss

@@ -4,7 +4,7 @@
 
 .accordion {
   // scss-docs-start accordion-css-vars
-  --#{$prefix}accordion-color: #{color-contrast($accordion-bg)};
+  --#{$prefix}accordion-color: #{$accordion-color};
   --#{$prefix}accordion-bg: #{$accordion-bg};
   --#{$prefix}accordion-transition: #{$accordion-transition};
   --#{$prefix}accordion-border-color: #{$accordion-border-color};