updated astro.md, next.md and removed luapress.md

Author: TomasBankauskas

src/site/generators/astro.md

@@ -18,6 +18,7 @@ templates:
   - Markdown
   - MDX
 description: Build faster websites with less client-side Javascript
+startertemplaterepo: https://github.com/netlify-templates/astro-platform-starter
 ---
 Astro is a fresh but familiar approach to building websites. 
 Astro combines decades of proven performance best practices with the DX improvements of the component-oriented era. 

src/site/generators/luapress.md

@@ -8,7 +8,7 @@ license:
   - MIT
 templates:
   - React
-startertemplaterepo: https://github.com/netlify-templates/next-netlify-starter
+startertemplaterepo: https://github.com/netlify-templates/next-platform-starter
 description: A framework for statically-exported React apps (supports server side rendering)
 twitter: nextjs
 ---