fix: change hooks testnet url

[pdp2121]

High Level Overview of Change

The hooks testnet url was changed a while ago but the previous one worked. That seems to have been disabled recently. New url is https://xahau-test.net

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (You added tests for code that already exists, or your new feature included in this PR)
• Documentation Updates
• Release

Did you update CHANGELOG.md?

• Yes
• No, this change does not impact library users