remove references to the hooks testnet faucet in xrpl.js codebase

[ckeshava]

High Level Overview of Change

as stated in the title

Context of Change

The reference to asf-flags pertaining to the Hooks amendment have not been removed.

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

Certain tests pertaining to hooks testnet faucet have been removed.

Did you update HISTORY.md?

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

Test Plan

No need to add additional tests, this PR removes code.