quickstart adjustments

Author: NoyaOffer

docs/_snippets/alerts/alerts-introduction.mdx

@@ -14,8 +14,8 @@ Custom channel, suppression interval, alert filters, etc.
 <Frame>
   <div className="dark:bg-white rounded-md p-4">
     <img
-      height ="320"
-      width="320"
+      height ="400"
+      width="400"
       src="https://res.cloudinary.com/dvmtceykh/image/upload/v1707742279/od5lminwcmktkjfh0lao.png"
       alt="Slack alert format"
     />