revise moonbeam rpc urls

[themacexpert]

What I did

Updated Moonbeam Endpoints because OnFinality is no longer supporting free public endpoints for Moonbeam, Moonriver, and Moonbase Alpha

For a full listing of all available Moonbeam network RPC urls, see here: https://docs.moonbeam.network/builders/get-started/endpoints/

How I did it

How to verify it

Checklist

• [ ] I have confirmed that my PR passes all linting checks
• [ ] I have included test cases
• [ ] I have updated the documentation
• [ ] I have added an entry to the changelog

[themacexpert]

@themacexpert I've modified them for the ones under moonbeam.network domain

Updated, thanks! 👍