docs: replace '(' with '{' in snippet tag (#685)

Author: 0x8b

apps/svelte.dev/content/tutorial/02-advanced-svelte/02-snippets/03-implicit-snippet-props/index.md

@@ -37,7 +37,7 @@ Any content inside a component that is _not_ part of a declared snippet becomes
 
 ```svelte
 /// file: App.svelte
----(#snippet header()}---
+---{#snippet header()}---
 <header>
 	<span class="color"></span>
 	<span class="name">name</span>