Frontend: fix class name when using Vue/JSX/Styles

Fixing a typo.

The CSS selector is `.title`, so `<h1 class={styles.title}>` will output something like `<h1 class="title_a3dKp">`, not `<h1 class="h1_a3dKp">`.

Author: Kocal

frontend/encore/vuejs.rst

@@ -129,7 +129,7 @@ a workaround, you can use `CSS Modules`_ by suffixing import paths with
         color: red
     }
 
-The output will be something like ``<h1 class="h1_a3dKp">Hello World</h1>``.
+The output will be something like ``<h1 class="title_a3dKp">Hello World</h1>``.
 
 Using images
 ~~~~~~~~~~~~