chore(deps): update tracing-opentelemetry requirement from 0.20 to 0.21

Updates the requirements on [tracing-opentelemetry](https://github.com/tokio-rs/tracing-opentelemetry) to permit the latest version.
- [Release notes](https://github.com/tokio-rs/tracing-opentelemetry/releases)
- [Changelog](https://github.com/tokio-rs/tracing-opentelemetry/blob/v0.1.x/CHANGELOG.md)
- [Commits](tokio-rs/tracing-opentelemetry@v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: tracing-opentelemetry
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

ledger/Cargo.toml

@@ -29,7 +29,7 @@ uuid = { version = "1.3", features = ["serde", "v4"] }
 rusty-money = { version = "0.4", features = ["iso", "crypto"] }
 tracing = "0.1"
 opentelemetry = { version =  "0.20", optional = true }
-tracing-opentelemetry = { version = "0.20", optional = true }
+tracing-opentelemetry = { version = "0.21", optional = true }
 cached = "0.44"