Bump the otel group with 1 update

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...v0.20.0)

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

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

Cargo.toml

@@ -37,7 +37,7 @@ required-features = ["json-logger"]
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 [dependencies]
-opentelemetry = {version = "0.20", features = ["rt-tokio"], optional = true}
+opentelemetry = {version = "0.21", features = ["rt-tokio"], optional = true}
 opentelemetry-otlp = {version = "0.13", features = ["http-proto", "reqwest-client"], default-features = false, optional = true}
 tracing = {version = "0.1", features = ["max_level_debug", "release_max_level_info"]}
 tracing-log = {version = "0.2"}