change(consensus): Updates post-NU6 Major Grants funding stream address on Mainnet

[arya2]

Motivation

We want to use the FPF address in the post-NU6 funding streams on Mainnet.

The minimum specified protocol version for NU6 on Mainnet is already correct, we'll need to update the CURRENT_NETWORK_PROTOCOL_VERSION in the release PR for v2.0.0, but not for the release candidate.

Specifications & References

https://zips.z.cash/zip-0214#direct-grant-option

Solution

• Updates the POST_NU6_FUNDING_STREAMS_MAINNET constant with the correct FPF address

PR Author's Checklist

• [ ] The PR name will make sense to users.
• [ ] The PR provides a CHANGELOG summary.
• [ ] The solution is tested.
• [ ] The documentation is up to date.
• [ ] The PR has a priority label.

PR Reviewer's Checklist

• [ ] The PR Author's checklist is complete.
• [ ] The PR resolves the issue.