chore: update deps to use zksync-contracts

[dutterbutter]

Description

• Updates contracts dep to make use of fresh zksync-contracts repo instead of v2-testnet-contracts beta branch

---

PR-Codex overview

This PR focuses on updating the submodules in the project by removing the lib/v2-testnet-contracts submodule and adding the lib/zksync-contracts submodule.

Detailed summary

• Deleted the submodule lib/v2-testnet-contracts.
• Added a new submodule lib/zksync-contracts with the path and URL specified.
• Updated remappings.txt to include era-contracts/ mapping to lib/zksync-contracts/contracts/.
• Modified .gitmodules to reflect the new submodule configuration.

✨ Ask PR-Codex anything about this PR by commenting with /codex {your question}

[coffeexcoin]

sorry - missed this PR - I actually did this in #9 after seeing the announcement