@andrea.zonca That error isn’t originating from Netlify, but seemingly from the GitHub API.
For unauthenticated requests, the rate limit allows for up to 60 requests per hour. Unauthenticated requests are associated with the originating IP address, and not the person making requests.
I’d read through their documentation and see if you can authorize your app, which comes with a higher rate limit, or otherwise adjust your app to work within the limits they apply.