Remove unnecessary code in "bind-this" example

In https://svelte.dev/examples#bind-this some code is superfluous

site/content/examples/05-bindings/10-bind-this/App.svelte

@@ -2,9 +2,6 @@
 	import { onMount } from 'svelte';
 
 	let canvas;
-	let running = false;
-
-	const r = Math.random();
 
 	onMount(() => {
 		const ctx = canvas.getContext('2d');