Update default testnet to Holesky, deprecate old testnets

[wackerow]

Description

• Removes any usage of Ropsten, Zhejiang or Goerli testnets (all deprecated)
• Updates Goerli references to use Holesky as the current default testnet

[netlify[bot]]

✅ Deploy Preview for dapper-rolypoly-9814ad ready!

Name	Link
🔨 Latest commit	03a5a0881c887600c379b84e87c5f9ab9fd7c737
🔍 Latest deploy log	https://app.netlify.com/sites/dapper-rolypoly-9814ad/deploys/668308cec1e6250008cb810d
😎 Deploy Preview	https://deploy-preview-701--dapper-rolypoly-9814ad.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.