docs: matches hint with existing structure and solution (#8915)

Author: chhotii-alex

documentation/tutorial/10-transitions/09-key-blocks/text.md

@@ -5,8 +5,10 @@ title: Key blocks
 Key blocks destroy and recreate their contents when the value of an expression changes.
 
 ```svelte
-{#key value}
-	<div transition:fade>{value}</div>
+{#key number}
+  <span style="display: inline-block" in:fade>
+    {number}
+  </span>
 {/key}
 ```