chore(deps): update dependency com_google_protobuf to v3.15.8 (#585)
chore(deps): update dependency com_google_protobuf to v3.15.8 (#585)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [com_google_protobuf](https://togithub.com/protocolbuffers/protobuf) | http_archive | patch | `v3.15.7` -> `v3.15.8` |

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### Release Notes

<details>
<summary>protocolbuffers/protobuf</summary>

### [`v3.15.8`](https://togithub.com/protocolbuffers/protobuf/releases/v3.15.8)

[Compare Source](https://togithub.com/protocolbuffers/protobuf/compare/v3.15.7...v3.15.8)

### Ruby

-   Fixed memory leak of Ruby arena objects ([#&#8203;8461](https://togithub.com/protocolbuffers/protobuf/issues/8461))

</details>

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