chore(deps): update dependency com_google_protobuf to v3.15.2 (#617)

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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 | `v3.15.1` -> `v3.15.2` |

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### Release Notes

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

### [`v3.15.2`](https://togithub.com/protocolbuffers/protobuf/releases/v3.15.2)

[Compare Source](https://togithub.com/protocolbuffers/protobuf/compare/v3.15.1...v3.15.2)

### Ruby

-   Fix for FieldDescriptor.get(msg) ([#&#8203;8330](https://togithub.com/protocolbuffers/protobuf/issues/8330))

### C++

-   Fix PROTOBUF_CONSTINIT macro redefinition ([#&#8203;8323](https://togithub.com/protocolbuffers/protobuf/issues/8323))

</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 = "5027403b91fea2376e26772bfd9ab323db1fe553c0f5bee502b8928ad1dd3bd2",
-  urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.15.1.zip"],
-  strip_prefix = "protobuf-3.15.1",
+  sha256 = "18b0a055105afc73d09948beec67b4b56d17ee55b0669cd105d246954adc59ae",
+  urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.15.2.zip"],
+  strip_prefix = "protobuf-3.15.2",
 )
 load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")
 protobuf_deps()