docs: fix broken links

Author: Fdawgs

README.md

@@ -545,9 +545,11 @@ fastify.post('/upload/files', async function (req, reply) {
 
 This project is kindly sponsored by:
 - [nearForm](https://nearform.com)
-- [LetzDoIt](https://www.letzdoitapp.com/)
 - [platformatic](https://platformatic.dev)
 
+Past sponsors:
+- LetzDoIt
+
 ## License
 
 Licensed under [MIT](./LICENSE).