fix(brand-band): Revert brand band gradient end stop to token value (#4644)

* revert brand band gradient end stop to token value

* update demo styles background value in brand band

Author: Dottenpixel

ui/components/brand-band/base/_index.scss

@@ -44,7 +44,7 @@
     top: 0;
     width: 100%;
     height: $brand-band-scrim-height;
-    background-image: linear-gradient(to bottom, $brand-background-primary-transparent 60%, #b0c4df);
+    background-image: linear-gradient(to bottom, $brand-background-primary-transparent 60%, $brand-background-primary);
   }
 
   /**

ui/components/brand-band/index.jsx

@@ -4,7 +4,7 @@
 import React, { Component } from 'react';
 import classNames from 'classnames';
 
-let tokenValue = 'rgb(176, 196, 223)';
+let tokenValue = '#eef4ff'; // BRAND_BACKGROUND_PRIMARY from design-tokens/aliases/color-palettes.yml
 
 export const BrandBand = props => (
   <div