docs(network-faucets): Chainstack faucet requirement is outdated — no longer uses API key

## Problem

File: docs/base-chain/network-information/network-faucets.mdx
Section: Chainstack Faucet

The current description states:

> "Chainstack Faucet dispenses Base ETH based on your Chainstack platform API key."

This is outdated. According to Chainstack's current faucet page (https://faucet.chainstack.com/base-testnet-faucet), the faucet no longer uses a platform API key. Instead, it now requires:

- A minimum balance of 0.08 ETH on Ethereum mainnet
- A history of holding ETH on mainnet (address should not have been recently empty)

## Expected behavior

Update the Chainstack Faucet description to reflect the current access requirements.

## References

- Chainstack Base faucet: https://faucet.chainstack.com/base-testnet-faucet