Remove unnecessary double quotes

This caused a bit of confusion for me when I first encountered it. (Because the rest of the tutorial doesn't care to use quotes unless its a string.

site/content/tutorial/05-events/02-inline-handlers/app-b/App.svelte

@@ -6,6 +6,6 @@
 	div { width: 100%; height: 100%; }
 </style>
 
-<div on:mousemove="{e => m = { x: e.clientX, y: e.clientY }}">
+<div on:mousemove={e => m = { x: e.clientX, y: e.clientY }}>
 	The mouse position is {m.x} x {m.y}
-</div>
+</div>