Update tutorial: Using Infura (or a custom provider) #1424

[anataliocs]

Issue: https://github.com/trufflesuite/trufflesuite.com/issues/1424

Updates for: https://trufflesuite.com/guides/using-infura-custom-provider/

• Update faucet to use new Infura Sepolia Faucet: https://www.infura.io/faucet/sepolia
• Update PROJECT ID to WEB3 API KEY.
• Update from Ropsten to Sepolia

[anataliocs]

Ready to merge?