Remove background from build state disabled

The build state disabled is a conscious decision and
therefore it is not necessary/too much to highlight it with
a background color.

src/api/app/assets/stylesheets/webui2/build-results.scss

@@ -45,9 +45,7 @@
 }
 
 .build-state-disabled {
-  @extend .text-white;
-  @extend .px-1;
-  background-color: $gray-600;
+  color: $gray-600;
 }
 
 .build-state-blocked {