chore(deps): update dependency com_google_protobuf to v3.21.8 (#1217)

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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 | `v3.21.5` -> `v3.21.8` |

---

### Release Notes

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

### [`v3.21.8`](https://togithub.com/protocolbuffers/protobuf/compare/v3.21.7...v3.21.8)

[Compare Source](https://togithub.com/protocolbuffers/protobuf/compare/v3.21.7...v3.21.8)

### [`v3.21.7`](https://togithub.com/protocolbuffers/protobuf/compare/v3.21.6...v3.21.7)

[Compare Source](https://togithub.com/protocolbuffers/protobuf/compare/v3.21.6...v3.21.7)

### [`v3.21.6`](https://togithub.com/protocolbuffers/protobuf/compare/v3.21.5...v3.21.6)

[Compare Source](https://togithub.com/protocolbuffers/protobuf/compare/v3.21.5...v3.21.6)

</details>

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WORKSPACE.bazel

@@ -35,9 +35,9 @@ switched_rules_by_language(name = "com_google_googleapis_imports", grpc = True)
 #
 http_archive(
   name = "com_google_protobuf",
-  sha256 = "8242327e5df8c80ba49e4165250b8f79a76bd11765facefaaecfca7747dc8da2",
-  urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.21.5.zip"],
-  strip_prefix = "protobuf-3.21.5",
+  sha256 = "3d76fb2f9401124a29879b3673464767427ad17c9ef57b15c0d7962824e83ac7",
+  urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.21.8.zip"],
+  strip_prefix = "protobuf-3.21.8",
 )
 load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")
 protobuf_deps()