Bump once_cell from 1.21.3 to 1.21.4 in /codex-rs

Bumps [once_cell](https://github.com/matklad/once_cell) from 1.21.3 to 1.21.4.
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](matklad/once_cell@v1.21.3...v1.21.4)

---
updated-dependencies:
- dependency-name: once_cell
  dependency-version: 1.21.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

codex-rs/Cargo.lock

@@ -311,7 +311,7 @@ mime_guess = "2.0.5"
 multimap = "0.10.0"
 notify = "8.2.0"
 nucleo = { git = "https://github.com/helix-editor/nucleo.git", rev = "4253de9faabb4e5c6d81d946a5e35a90f87347ee" }
-once_cell = "1.20.2"
+once_cell = "1.21.4"
 openssl-sys = "*"
 opentelemetry = "0.31.0"
 opentelemetry-appender-tracing = "0.31.0"