Update parking_lot requirement from 0.11.2 to 0.12.0

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](https://github.com/Amanieu/parking_lot/compare/0.11.2...0.12.0)

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

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

Cargo.toml

@@ -37,7 +37,7 @@ jemallocator = "0.3.2"
 libsodium-sys-stable = "1.19.19"
 log = { version = "0.4.14", features = ["std", "release_max_level_debug"] }
 socket2 = "0.4.2"
-parking_lot = "0.11.2"
+parking_lot = "0.12.0"
 privdrop = "0.5.1"
 rand = "0.8.4"
 rustc-hash = "1.1.0"