Fix broken link to developper portal in README.md

Author: pollastri-pierre

README.md

@@ -49,7 +49,7 @@ Ledger Blue is not maintained anymore, but the app can still be compiled for thi
 
 This app follows the specification available in the `doc/` folder.
 
-To compile it and load it on a device, please check out our [developer portal](https://developers.ledger.com/docs/nano-app/introduction/).
+To compile it and load it on a device, please check out our [developer portal](https://developers.ledger.com/docs/device-app/introduction).
 
 ### Plugins