…1.21.0 (#1876)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [@opentelemetry/semantic-conventions](https://togithub.com/open-telemetry/opentelemetry-js/tree/main/packages/opentelemetry-semantic-conventions) ([source](https://togithub.com/open-telemetry/opentelemetry-js)) | [`~1.20.0` -> `~1.21.0`](https://renovatebot.com/diffs/npm/@opentelemetry%2fsemantic-conventions/1.20.0/1.21.0) | [![age](https://developer.mend.io/api/mc/badges/age/npm/@opentelemetry%2fsemantic-conventions/1.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/@opentelemetry%2fsemantic-conventions/1.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/@opentelemetry%2fsemantic-conventions/1.20.0/1.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/@opentelemetry%2fsemantic-conventions/1.20.0/1.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

<details>
<summary>open-telemetry/opentelemetry-js (@&#8203;opentelemetry/semantic-conventions)</summary>

### [`v1.21.0`](https://togithub.com/open-telemetry/opentelemetry-js/blob/HEAD/CHANGELOG.md#1210)

[Compare Source](https://togithub.com/open-telemetry/opentelemetry-js/compare/v1.20.0...v1.21.0)

##### 🚀 (Enhancement)

-   feat(sdk-metrics): add constructor option to add metric readers [#&#8203;4427](https://togithub.com/open-telemetry/opentelemetry-js/pull/4427) [@&#8203;pichlermarc](https://togithub.com/pichlermarc)
    -   deprecates `MeterProvider.addMetricReader()` please use the constructor option `readers` instead.

##### 🐛 (Bug Fix)

-   fix(sdk-trace-base): ensure attribute value length limit is enforced on span creation [#&#8203;4417](https://togithub.com/open-telemetry/opentelemetry-js/pull/4417) [@&#8203;pichlermarc](https://togithub.com/pichlermarc)
-   fix(sdk-trace-base): Export processed spans while exporter failed [#&#8203;4287](https://togithub.com/open-telemetry/opentelemetry-js/pull/4287) [@&#8203;Zirak](https://togithub.com/Zirak)

##### 🏠 (Internal)

-   chore(opentelemetry-context-zone-peer-dep): support zone.js ^v0.13.0 [#&#8203;4320](https://togithub.com/open-telemetry/opentelemetry-js/pull/4320)
-   refactor(core): drop unnecessary assignment of HOSTNAME [#&#8203;4421](https://togithub.com/open-telemetry/opentelemetry-js/pull/4421) [@&#8203;pichlermarc](https://togithub.com/pichlermarc)
-   test(opentelemetry-context-zone-peer-dep): transpile zone.js in tests [#&#8203;4423](https://togithub.com/open-telemetry/opentelemetry-js/pull/4423) [@&#8203;legendecas](https://togithub.com/legendecas)

</details>

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