docs: minor grammar cleanup (#538)

Author: Michael Baker

content/tutorial/03-sveltekit/08-stores/03-updated-store/README.md

@@ -4,7 +4,7 @@ title: updated
 
 The `updated` store contains `true` or `false` depending on whether a new version of the app has been deployed since the page was first opened. For this to work, your `svelte.config.js` must specify `kit.version.pollInterval`.
 
-Version changes only happens in production, not during development. For that reason, `$updated` will always be `false` in this tutorial.
+Version changes only happen in production, not during development. For that reason, `$updated` will always be `false` in this tutorial.
 
 You can manually check for new versions, regardless of `pollInterval`, by calling `updated.check()`.