docs: Make "unquoted" example actually unquoted (#8937)

Author: danawoodman

documentation/docs/02-template-syntax/02-basic-markup.md

@@ -28,8 +28,9 @@ By default, attributes work exactly like their HTML counterparts.
 
 As in HTML, values may be unquoted.
 
+<!-- prettier-ignore -->
 ```svelte
-<input type="checkbox" />
+<input type=checkbox />
 ```
 
 Attribute values can contain JavaScript expressions.