chore: Update header post ArgoCon EU 2025 (#183)

Signed-off-by: Oliver Gondža <ogondza@gmail.com>

Author: olivergondza

src/components/header.js

@@ -26,8 +26,8 @@ const Header = ({ color }) => {
     <React.Fragment>
 
       <div className="announcement-banner bg-[#302871] py-3">
-        <a href="https://events.linuxfoundation.org/kubecon-cloudnativecon-europe/co-located-events/argocon/">
-          Join us at ArgoCon EU 2025, colocated with KubeCon/CloudNativeCon 2025 London. Register now!
+        <a href="https://www.youtube.com/playlist?list=PLj6h78yzYM2N9MWCsU_4upn64NDtHGv6i">
+          ArgoCon EU 2025 Is a Wrap, watch the talks on Youtube.
           <svg class="HoverArrow" width="10" height="10" viewBox="0 0 10 10" aria-hidden="true">
             <g fill-rule="evenodd">
             <path class="HoverArrow__linePath" d="M0 5h7"></path>