Upgrade Rust toolchain to 1.84.0

[MichaReiser]

Summary

Upgrade the rust toolchain to 1.84.0. This PR does not bump the MSRV.

Test Plan

cargo test

[MichaReiser]

    Checking ruff v0.9.1 (/Users/micha/astral/ruff/crates/ruff)
warning: allocating a local array larger than 16384 bytes
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#large_stack_arrays
  = note: `-W clippy::large-stack-arrays` implied by `-W clippy::pedantic`
  = help: to override `-W clippy::pedantic` add `#[allow(clippy::large_stack_arrays)]`

warning: `ruff_linter` (lib test) generated 1 warning

but ruff_linter is kind of big.

I subscribed to the issue

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

ℹ️ ecosystem check encountered format errors. (no format changes; 1 project error)

openai/openai-cookbook (error)

warning: Detected debug build without --no-cache.
error: Failed to read examples/Assistants_API_overview_python.ipynb: Expected a Jupyter Notebook, which must be internally stored as JSON, but this file isn't valid JSON: expected `,` or `]` at line 197 column 8

Formatter (preview)

ℹ️ ecosystem check encountered format errors. (no format changes; 1 project error)

openai/openai-cookbook (error)

ruff format --preview

warning: Detected debug build without --no-cache.
error: Failed to read examples/Assistants_API_overview_python.ipynb: Expected a Jupyter Notebook, which must be internally stored as JSON, but this file isn't valid JSON: expected `,` or `]` at line 197 column 8