fix: remove nested sitemap index reference

Remove api/sitemaps/index.xml from static sitemap.xml to fix
Google Search Console "nested indexing" error. The dynamic
sitemap index will be submitted separately.

Author: idoshamun

packages/webapp/public/sitemap.xml

@@ -3,7 +3,4 @@
   <sitemap>
     <loc>https://app.daily.dev/sitemap.txt</loc>
   </sitemap>
-  <sitemap>
-    <loc>https://app.daily.dev/api/sitemaps/index.xml</loc>
-  </sitemap>
 </sitemapindex>