[portal] fix Tailwind style ordering issue

apps/portal/postcss.config.cjs

@@ -1,13 +1,6 @@
-// If you want to use other PostCSS plugins, see the following:
-// https://tailwindcss.com/docs/using-with-preprocessors
-
-const config = require('@tih/tailwind-config/tailwind.config.js');
-
 module.exports = {
   plugins: {
-    // Specifying the config is not necessary in most cases, but it is included
-    // here to share the same config across the entire monorepo
-    tailwindcss: { config },
+    tailwindcss: {},
     autoprefixer: {},
   },
 };