build(deps): bump once_cell from 1.10.0 to 1.12.0

Bumps [once_cell](https://github.com/matklad/once_cell) from 1.10.0 to 1.12.0.
- [Release notes](https://github.com/matklad/once_cell/releases)
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](https://github.com/matklad/once_cell/compare/v1.10.0...v1.12.0)

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

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

helix-loader/Cargo.toml

@@ -15,7 +15,7 @@ serde = { version = "1.0", features = ["derive"] }
 toml = "0.5"
 etcetera = "0.4"
 tree-sitter = "0.20"
-once_cell = "1.9"
+once_cell = "1.12"
 
 log = "0.4"