chore: adjust banner color

Author: denolfe

src/admin/components/elements/Banner/index.scss

@@ -5,7 +5,7 @@
   line-height: base(1);
   border: 0;
   vertical-align: middle;
-  background: var(--theme-elevation-900);
+  background: var(--theme-elevation-100);
   color: var(--theme-elevation-800);
   border-radius: $style-radius-s;
   padding: base(.5);