revert change in postcss fixture

Author: philipp-spiess

packages/@tailwindcss-postcss/src/fixtures/example-project/src/relative-import.css

@@ -1,4 +1 @@
-/* @plugin '../plugin.js'; */
-.foo {
-  @apply text-red-500;
-}
+@plugin '../plugin.js';

packages/@tailwindcss-postcss/src/index.test.ts

@@ -197,7 +197,15 @@ describe('plugins', () => {
         }
       }
 
-      @apply text-red-500;
+      @media (inverted-colors: inverted) {
+        .inverted\\:flex {
+          display: flex;
+        }
+      }
+
+      .hocus\\:underline:focus, .hocus\\:underline:hover {
+        text-decoration-line: underline;
+      }
 
       @supports (-moz-orient: inline) {
         @layer base {