use right brand color in test

Author: cscheid

tests/docs/smoke-all/brand/test-01/test_brand.lua

@@ -1,6 +1,6 @@
 local brand = require("modules/brand/brand")
 
 function Pandoc(doc)
-  assert(brand.get_color("primary") == "#FF0000")
+  assert(brand.get_color("primary") == "#ff0000")
   return doc
 end