Update Rust crate tracing-opentelemetry to 0.21

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
tracing-opentelemetry	dev-dependencies	minor	0.20 -> 0.21

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Release Notes

tokio-rs/tracing-opentelemetry (tracing-opentelemetry)

### [`v0.21.0`](https://togithub.com/tokio-rs/tracing-opentelemetry/blob/HEAD/CHANGELOG.md#0210-August-28-2023) [Compare Source](https://togithub.com/tokio-rs/tracing-opentelemetry/compare/v0.20.0...v0.21.0) ##### Added - Ability to produce measurement with attributes ([#​43](https://togithub.com/tokio-rs/tracing-opentelemetry/issues/43)) ##### Breaking Changes - `MetricsLayer` is now generic over the its `Subscriber` impl to support [per-layer filtering] ([#​43](https://togithub.com/tokio-rs/tracing-opentelemetry/issues/43)) ##### Fixed - Trace IDs not matching when propagating invalid contexts ([#​55](https://togithub.com/tokio-rs/tracing-opentelemetry/issues/55)) Thanks to [@​ymgyt](https://togithub.com/ymgyt) and [@​hdost](https://togithub.com/hdost) for contributing to this release! [per-layer filtering]: https://docs.rs/tracing-subscriber/0.3.17/tracing_subscriber/layer/index.html#per-layer-filtering

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