build(deps): update parking_lot requirement from 0.11.2 to 0.12.0 (#1878

)

Updates the requirements on [parking_lot](https://github.com/Amanieu/parking_lot) to permit the latest version.
- [Release notes](https://github.com/Amanieu/parking_lot/releases)
- [Changelog](https://github.com/Amanieu/parking_lot/blob/master/CHANGELOG.md)
- [Commits](Amanieu/parking_lot@0.11.2...0.12.0)

---
updated-dependencies:
- dependency-name: parking_lot
  dependency-type: direct:production
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Eliza Weisman <eliza@buoyant.io>

tracing-appender/Cargo.toml

@@ -23,7 +23,7 @@ rust-version = "1.53.0"
 [dependencies]
 crossbeam-channel = "0.5.0"
 time = { version = "0.3", default-features = false, features = ["formatting"] }
-parking_lot = { optional = true, version = "0.11.2" }
+parking_lot = { optional = true, version = "0.12.0" }
 
 [dependencies.tracing-subscriber]
 path = "../tracing-subscriber"