Fix form link (#1182)

Author: clytaemnestra

src/content/pages/beginners-day.mdx

@@ -23,7 +23,7 @@ The number of places available for each track is as follows:
 
 <div class="text-center">
 
-<ButtonLink url="https://forms.gle/T8da5sQbKn6BFsxH7">Apply for Beginners' Day!</ButtonLink>
+<ButtonLink url="https://forms.gle/6mGPPEFMrLsxqHJx5">Apply for Beginners' Day!</ButtonLink>
 
 </div>