chore: update filecoin-ffi back to v1.34.0

[rjan90]

Proposed Changes

Filecoin-FFI was updated to v1.34.0 in #13336, but #13339 which landed later but most likely was branched off before the FFI bump, changed the FFI-version back to v1.34.0-dev.

This PR changes it back to the v1.34.0 version: https://github.com/filecoin-project/filecoin-ffi/releases/tag/v1.34.0

Checklist

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

• Commits have a clear commit message.
• PR title conforms with contribution conventions
• Update CHANGELOG.md or signal that this change does not need it per contribution conventions
• 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

[Copilot]

Pull Request Overview

Update the filecoin-ffi submodule pointer to the released v1.34.0 commit (reverting a prior -dev pointer).

• Point submodule to commit for v1.34.0 release
• Remove reference to v1.34.0-dev

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