docs: remove extraneous dash (#13105)

Author: arty-name

documentation/docs/20-core-concepts/10-routing.md

@@ -169,7 +169,7 @@ To create a layout that applies to every page, make a file called `src/routes/+l
 ...but we can add whatever markup, styles and behaviour we want. The only requirement is that the component includes a `@render` tag for the page content. For example, let's add a nav bar:
 
 ```svelte
-<!---- file: src/routes/+layout.svelte --->
+<!--- file: src/routes/+layout.svelte --->
 <script>
 	let { children } = $props();
 </script>