Update opentelemetry requirement from 0.20.0 to 0.21.0

Updates the requirements on [opentelemetry](https://github.com/open-telemetry/opentelemetry-rust) to permit the latest version.
- [Release notes](https://github.com/open-telemetry/opentelemetry-rust/releases)
- [Commits](open-telemetry/opentelemetry-rust@v0.20.0...v0.21.0)

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

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

Cargo.toml

@@ -11,7 +11,7 @@ toml = "0.8.0"
 anyhow = "1.0.53"
 tracing = { version = "0.1.30", features = ["attributes"] }
 tracing-subscriber = { version = "0.3.8", features = ["env-filter"] }
-opentelemetry = "0.20.0"
+opentelemetry = "0.21.0"
 opentelemetry-jaeger = "0.19.0"
 tracing-opentelemetry = "0.21.0"