deps: update dependency com.google.protobuf:protobuf-bom to v3.21.4 (#…

…877)

[![Mend Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.protobuf:protobuf-bom](https://developers.google.com/protocol-buffers/) ([source](https://github.com/protocolbuffers/protobuf)) | `3.21.3` -> `3.21.4` | [![age](https://badges.renovateapi.com/packages/maven/com.google.protobuf:protobuf-bom/3.21.4/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.protobuf:protobuf-bom/3.21.4/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.protobuf:protobuf-bom/3.21.4/compatibility-slim/3.21.3)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.protobuf:protobuf-bom/3.21.4/confidence-slim/3.21.3)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v3.21.4`](https://github.com/protocolbuffers/protobuf/compare/v3.21.3...v3.21.4)

[Compare Source](https://github.com/protocolbuffers/protobuf/compare/v3.21.3...v3.21.4)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click this checkbox.

---

This PR has been generated by [Mend Renovate](https://www.mend.io/free-developer-tools/renovate/). View repository job log [here](https://app.renovatebot.com/dashboard#github/googleapis/java-core).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzMi4xMjcuNCIsInVwZGF0ZWRJblZlciI6IjMyLjEyNy40In0=-->

java-core/pom.xml

@@ -159,7 +159,7 @@
     <google.api.version>2.0.0</google.api.version>
     <google.http.version>1.42.2</google.http.version>
     <grpc.version>1.48.0</grpc.version>
-    <protobuf.version>3.21.3</protobuf.version>
+    <protobuf.version>3.21.4</protobuf.version>
     <opencensus.version>0.31.1</opencensus.version>
     <annotations-api.version>1.3.2</annotations-api.version>
     <guava.version>31.1-jre</guava.version>