chore: updated zksync era dependency to v6.0.0

[mm-zk]

What 💻

• Updated the dependency on zksync-era to v6
• this is basically the same as we use today, so there are no changes.

Why ✋

• zksync era is doing a major release, that contains a large VM api change
• so we have to clean up our dependency versions, so that era-test-node doesn't get broken
• as previous commit of zksync-era that we depended on, have sub-dependencies that will be broken soon

Evidence 📷

[MexicanAce]

LGTM