Update opentelemetry requirement from 0.18 to 0.27

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@opentelemetry-0.18.0...opentelemetry-0.20.0)

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

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

Cargo.toml

@@ -10,7 +10,7 @@ readme = "README.md"
 keywords = ["middleware", "datadog", "axum", "hyper", "opentelemetry"]
 
 [dependencies]
-opentelemetry = { version = "0.18", features = ["rt-tokio"] }
+opentelemetry = { version = "0.27", features = ["rt-tokio"] }
 opentelemetry-datadog = { version = "0.6", features = ["reqwest-client"] }
 opentelemetry-semantic-conventions = "0.10"
 tower = { version = "0.4", features = ["util"] }