docs: update Svelte version to 4 (sveltejs#412)

fixes sveltejs#413

Author: rashedjawda

content/tutorial/01-svelte/03-props/03-spread-props/app-a/src/lib/App.svelte

@@ -4,7 +4,7 @@
 	const pkg = {
 		name: 'svelte',
 		speed: 'blazing',
-		version: 3,
+		version: 4,
 		website: 'https://svelte.dev'
 	};
 </script>

content/tutorial/01-svelte/03-props/03-spread-props/app-b/src/lib/App.svelte

@@ -4,7 +4,7 @@
 	const pkg = {
 		name: 'svelte',
 		speed: 'blazing',
-		version: 3,
+		version: 4,
 		website: 'https://svelte.dev'
 	};
 </script>