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>

Cargo.toml

@@ -46,7 +46,7 @@ ansi_colours = "^1.1"
 bincode = "1.0"
 console = "0.15.0"
 flate2 = "1.0"
-once_cell = "1.10"
+once_cell = "1.12"
 thiserror = "1.0"
 wild = { version = "2.0", optional = true }
 content_inspector = "0.2.4"