deps: ffi: update ffi to 280c4f8b94fd46dc

[jennijuju]

Additional Info

integrate with the ffi master for monthly release testing flow

ffi branch https://github.com/filecoin-project/filecoin-ffi/tree/release/lotus-v1.19.0

Checklist

Before you mark the PR ready for review, please make sure that:

• Commits have a clear commit message.
• PR title is in the form of of <PR type>: <area>: <change being made>
  • example: fix: mempool: Introduce a cache for valid signatures
  • PR type: fix, feat, build, chore, ci, docs, perf, refactor, revert, style, test
  • area, e.g. api, chain, state, market, mempool, multisig, networking, paych, proving, sealing, wallet, deps
• New features have usage guidelines and / or documentation updates in
  • Lotus Documentation
  • Discussion Tutorials
• Tests exist for new functionality or change in behavior
• CI is green