Change websafe sass param to contrast-safe

https://github.com/alphagov/govuk-frontend/blob/main/CHANGELOG.md#weve-updated-the-list-of-organisations-and-brand-colours-included-in-frontend

Author: AshGDS

app/assets/stylesheets/govuk_publishing_components/components/helpers/_brand-colours.scss

@@ -20,7 +20,7 @@
       // element as required by the heading component, adds 2KB to the CSS
       &.brand__border-color,
       .brand__border-color {
-        border-color: govuk-organisation-colour($organisation, $websafe: false);
+        border-color: govuk-organisation-colour($organisation, $contrast-safe: false);
       }
     }
   }
@@ -49,7 +49,7 @@
 
   &.brand__border-color,
   .brand__border-color {
-    border-color: govuk-organisation-colour("office-of-the-leader-of-the-house-of-commons", $websafe: false);
+    border-color: govuk-organisation-colour("office-of-the-leader-of-the-house-of-commons", $contrast-safe: false);
   }
 }
 // colours for the prime ministers office are not included in the toolkit